Quick Recipe Version (TL;DR)

Yield: 12 generous slices
Prep Time: 45 minutes (plus cooling)
Cook Time: 30–35 minutes
Total Time: About 2 hours 30 minutes

Quick Ingredients

1 cup (226 g) unsalted butter, plus extra for pans
16 oz (455 g) semisweet chocolate, chopped (divided for brownies and ganache)
2 cups (400 g) granulated sugar
1/2 cup (100 g) packed light brown sugar
4 large eggs, room temp
1 1/2 tsp vanilla extract (plus extra for buttercream)
1 cup (120 g) all-purpose flour
3/4 cup (65 g) unsweetened cocoa powder (divided for brownies and buttercream)
3/4 tsp fine salt (plus pinch for buttercream)
1 1/2 cups (360 ml) heavy cream
1 cup (226 g) unsalted butter, softened (for buttercream)
3 cups (360 g) powdered sugar
Optional: espresso powder, flaky sea salt, berries, extra brownie chunks for garnish

Do This

1. Heat oven to 350°F (175°C). Grease and line two 8-inch round cake pans with parchment.
2. Melt butter and 8 oz chocolate; whisk in sugars, eggs, vanilla, then flour, cocoa, and salt. Divide between pans and bake 25–30 minutes. Cool completely.
3. Make ganache: pour hot cream over 8 oz chopped chocolate, rest 2–3 minutes, then stir smooth. Cool until thick but spreadable.
4. Make buttercream: beat 1 cup butter until creamy, then mix in powdered sugar, cocoa, salt, vanilla, and enough cream for a smooth, fluffy frosting.
5. Level brownie layers if needed. Place first layer on a plate, spread with a thin layer of ganache, then a thicker layer of chocolate buttercream.
6. Top with second brownie layer, crumb-coat with buttercream, chill briefly, then frost sides and top smoothly.
7. Pour remaining ganache over the top, letting it drip slightly. Decorate with brownie chunks, chocolate shavings, and a pinch of flaky sea salt.

Why You’ll Love This Recipe

It is ultra-fudgy and dense like your favorite brownies, but looks and slices like a celebration cake.
Triple chocolate: brownie layers, silky ganache, and fluffy chocolate buttercream for maximum chocolate flavor.
Brownie chunks and ganache on top give it a dramatic, bakery-style finish with very little fuss.
The components can be made ahead, so it is perfect for birthdays, holidays, and special occasions.

Grocery List

Produce: Fresh berries and/or mint sprigs for serving (optional)
Dairy: Unsalted butter, heavy cream, eggs
Pantry: Granulated sugar, light brown sugar, powdered sugar, all-purpose flour, unsweetened cocoa powder, semisweet chocolate, vanilla extract, fine salt, espresso powder (optional), nonstick spray or extra butter for pans

Full Ingredients

For the Brownie Layers (two 8-inch rounds)

1 cup (226 g) unsalted butter, cut into pieces
8 oz (225 g) semisweet chocolate, finely chopped
2 cups (400 g) granulated sugar
1/2 cup (100 g) packed light brown sugar
4 large eggs, at room temperature
2 tsp vanilla extract
1 tsp instant espresso powder (optional, enhances chocolate flavor)
1 cup (120 g) all-purpose flour, spooned and leveled
1/2 cup (45 g) unsweetened cocoa powder (natural or Dutch-process)
3/4 tsp fine sea salt or table salt
Butter or nonstick spray and cocoa powder, for preparing the pans

For the Chocolate Ganache (filling and topping)

8 oz (225 g) semisweet chocolate, finely chopped
1 1/2 cups (360 ml) heavy cream
2 tbsp (28 g) unsalted butter, at room temperature
1/2 tsp vanilla extract
Pinch of fine salt

For the Chocolate Buttercream

1 cup (226 g) unsalted butter, very soft but not melted
3 cups (360 g) powdered sugar, sifted
1/4 cup (20 g) unsweetened cocoa powder
1/4 cup (25 g) Dutch-process cocoa powder (for deeper color and flavor; or use all regular cocoa)
1/4 tsp fine salt
2–4 tbsp (30–60 ml) heavy cream or milk, plus more as needed
2 tsp vanilla extract

For Assembly & Decoration

Extra brownie pieces from trimming the layers, cut into chunks
Chocolate shavings or curls (optional)
Flaky sea salt (optional, but highly recommended)
Fresh berries or mint sprigs, for serving (optional)

Step-by-Step Instructions

Step 1: Prepare the pans and preheat the oven

Preheat your oven to 350°F (175°C) with a rack in the center. Grease two 8-inch (20 cm) round cake pans with butter or nonstick spray. Line the bottoms with parchment paper circles, then grease the parchment as well. Dust the sides lightly with cocoa powder, tapping out any excess. This will help the brownie layers release easily and keep the edges dark and chocolatey instead of floury.

Step 2: Make the ultra-fudgy brownie batter

Place the 1 cup (226 g) butter and 8 oz (225 g) chopped semisweet chocolate in a heatproof bowl. Melt together over a saucepan of gently simmering water (double-boiler style), stirring often, until completely smooth. Alternatively, microwave in 20–30 second bursts, stirring between each, until melted and glossy. Remove from heat and let cool for 3–5 minutes so it is warm but not hot.

Whisk in the granulated sugar and brown sugar until thick and shiny. Add the eggs one at a time, whisking well after each addition. Whisk in the vanilla and espresso powder (if using); the batter should look thick and smooth.

In a separate bowl, whisk together the flour, cocoa powder, and salt. Add the dry ingredients to the chocolate mixture and fold gently with a spatula just until no dry streaks remain. The batter will be quite thick and glossy; avoid overmixing so the brownies stay dense and chewy.

Step 3: Bake the brownie layers

Divide the brownie batter evenly between the two prepared pans (a kitchen scale is helpful for very even layers). Smooth the tops with an offset spatula or the back of a spoon. Tap each pan firmly on the counter a couple of times to release any large air bubbles.

Bake for 25–30 minutes, rotating the pans halfway through, until the edges are set and slightly pulled away from the pan, and a toothpick inserted into the center comes out with moist crumbs but no wet batter. Remember: slightly underbaked is better than overbaked for fudgy brownies.

Place the pans on a wire rack and let the brownies cool completely in the pans, at least 1 hour. Once cool, run a knife around the edges, invert onto a rack, and peel off the parchment. If the tops are very domed, you can level them with a serrated knife and save the trimmings for decoration.

Step 4: Make the silky chocolate ganache

While the brownie layers cool, place 8 oz (225 g) finely chopped semisweet chocolate in a heatproof bowl. In a small saucepan, heat the heavy cream over medium heat until it is steaming and just starting to bubble around the edges, but not boiling. Immediately pour the hot cream over the chopped chocolate. Let sit undisturbed for 2–3 minutes to soften.

After resting, gently whisk from the center outward until the mixture is smooth and glossy. Add the butter, vanilla, and a pinch of salt, whisking until completely combined. If any bits of chocolate remain, warm the bowl briefly over a pan of hot (not boiling) water and stir until melted.

Set the ganache aside at room temperature to thicken. For filling and dripping, you are aiming for a consistency similar to soft pudding: thick but still pourable. This usually takes 20–30 minutes; you can refrigerate it for a few minutes to speed things up, stirring often so it thickens evenly.

Step 5: Make the chocolate buttercream

In a large mixing bowl, beat the 1 cup (226 g) softened butter with a hand mixer or stand mixer on medium speed for 2–3 minutes, until very creamy and slightly paler in color. In a separate bowl, whisk together the powdered sugar, cocoa powders, and salt.

With the mixer on low, gradually add the cocoa–sugar mixture to the butter, about 1/2 cup at a time, mixing until incorporated before adding more. The mixture will be thick. Add the vanilla and 2 tbsp of the cream or milk, then increase the mixer speed to medium-high and beat for 2–3 minutes, until light, smooth, and fluffy. If the buttercream seems too thick, add more cream 1 tablespoon at a time; if it is too soft, add a little more powdered sugar. You want a consistency that holds its shape but spreads easily.

Step 6: Level and fill the brownie cake

If you have not already, level the tops of the brownie layers with a long serrated knife, keeping the knife as flat as possible. Save any trimmings and cut them into bite-sized chunks for decorating the top later.

Place one brownie layer, cut side up, on a serving plate or cake stand. If you like, secure it with a small smear of buttercream underneath. Stir the ganache and check its texture: it should be thick but scoopable, not runny. Spread a thin layer of ganache over the top of the first layer (about 1/2 cup), leaving a small border around the edge. This fills in any gaps and adds extra fudginess.

Dollop a generous amount of chocolate buttercream on top of the ganache (about 1 to 1 1/2 cups) and spread evenly to the edges. Place the second brownie layer on top, cut side down, and gently press to level. If any buttercream squeezes out, smooth it around the sides for a light crumb coat.

Step 7: Frost the outside and add the ganache topping

Use a thin layer of buttercream to crumb-coat the sides and top of the cake: spread a light coat that catches any loose crumbs. Chill the cake in the refrigerator for 15–20 minutes until the buttercream is firm. This step makes it much easier to get a clean final coat.

Once chilled, apply the remaining buttercream to the sides and top of the cake, smoothing with an offset spatula or bench scraper. The cake does not have to be perfect; a slightly rustic finish suits this style very well.

If your ganache has become too thick to pour, warm it briefly over a bowl of hot water or in the microwave for 5–10 seconds and stir until it is pourable but still thick. Pour most of the ganache onto the center of the cake and gently nudge it toward the edges with a spatula, allowing it to drip slightly down the sides for a dramatic look. Reserve a little ganache to drizzle over the brownie chunks later, if you like.

Step 8: Decorate with brownie chunks and serve

While the ganache is still soft, arrange the reserved brownie chunks in a loose pile or ring on top of the cake. Drizzle with any remaining ganache. Add chocolate shavings or curls and a light sprinkle of flaky sea salt for contrast. If using, tuck in a few fresh berries or mint sprigs right before serving.

Refrigerate the cake for at least 30 minutes to help everything set for clean slices. For serving, run a sharp knife under hot water, wipe dry, and cut into generous slices. This cake is very rich; 12 servings are usually plenty. Enjoy slightly chilled or at cool room temperature for the best texture.

Pro Tips

For the fudgiest texture, do not overbake the brownie layers. Pull them from the oven when a toothpick still shows a few moist crumbs.
Use good-quality chocolate (at least 50–60 percent cocoa) for both the brownies and ganache; it makes a huge difference in flavor.
Make sure the brownie layers are completely cool before stacking, or the buttercream and ganache will melt and slide.
If your buttercream looks grainy, keep beating; it usually smooths out with a few extra minutes of mixing and a splash more cream.
For very neat layers, chill the filled cake for 20–30 minutes before adding the final coat of buttercream and ganache.

Variations

Salted Caramel Brownie Cake: Spread a thin layer of thick salted caramel over the first brownie layer before adding the buttercream, and drizzle caramel over the top along with the ganache.
Mocha Brownie Cake: Add 2–3 tsp espresso powder to the brownie batter and 1–2 tsp to the buttercream for a rich coffee–chocolate flavor.
Peanut Butter Twist: Swirl 1/2 cup warmed peanut butter into the ganache before it sets, and dot the top with chopped roasted peanuts along with the brownie chunks.

Storage & Make-Ahead

The assembled cake keeps well, covered, in the refrigerator for up to 4 days. For the best flavor and texture, let slices sit at room temperature for 20–30 minutes before serving so the brownie layers soften slightly and the buttercream loses its chill.

You can make the brownie layers up to 2 days ahead: wrap cooled layers tightly in plastic and store at room temperature, or freeze for up to 2 months (thaw, still wrapped, in the fridge overnight). The buttercream can be made 2–3 days in advance and stored in an airtight container in the fridge; bring to room temperature and re-whip briefly before using. Ganache can be made 1–2 days ahead and gently rewarmed to a pourable consistency over a bowl of hot water or in short microwave bursts.

Nutrition (per serving)

Approximate for 1 of 12 servings: 900 calories; 60 g fat; 35 g saturated fat; 105 mg cholesterol; 105 g carbohydrates; 5 g fiber; 80 g sugars; 10 g protein; 420 mg sodium. These values are estimates and will vary based on specific ingredients and portion sizes.

Ultimate Fudgy Brownie Layer Cake with Ganache Buttercream