Quick Recipe Version (TL;DR)
Quick Ingredients
- 2 1/4 cups (270 g) all-purpose flour
- 2 1/2 tsp baking powder, 1/2 tsp fine salt
- 1 1/2 cups (300 g) granulated sugar
- 1/2 cup (115 g) unsalted butter, plus 2 tbsp for pastry cream and 2 tbsp for ganache
- 1/4 cup (60 ml) neutral oil (canola or vegetable)
- 4 large eggs (plus 6 large yolks for pastry cream)
- 3 1/2 cups (840 ml) whole milk, divided
- 1 1/2 cups (360 ml) heavy cream, divided
- 1/4 cup (30 g) cornstarch
- 10 2/3 oz (300 g) semisweet or dark chocolate, finely chopped
- 4 tsp pure vanilla extract
- Pinch of salt, 1 tsp light corn syrup (optional)
Do This
- 1. Make pastry cream: Whisk yolks, sugar, cornstarch, and salt; cook with hot milk/cream until thick, then whisk in butter and vanilla. Chill completely.
- 2. Heat oven to 350°F (175°C). Grease and line two 9-inch round cake pans.
- 3. Cream butter, oil, and sugar; beat in eggs and vanilla. Add dry ingredients alternately with milk to make a smooth batter.
- 4. Divide batter between pans and bake 24–28 minutes until golden and a tester comes out clean. Cool completely.
- 5. Level cakes if needed. Place one layer on a stand, pipe or spread a dam of pastry cream, then fill and top with second layer.
- 6. Make ganache by pouring hot cream over chopped chocolate and butter; stir smooth. Cool to a pourable, thick-but-flowy consistency.
- 7. Pour ganache over chilled cake, letting it drip down the sides. Chill briefly to set before slicing.
Why You’ll Love This Recipe
- All the nostalgic flavor of classic Boston cream pie, reimagined as an elegant layer cake.
- Soft, tender vanilla sponge, silky pastry cream, and glossy chocolate ganache in every bite.
- Make-ahead friendly: the pastry cream and cake layers can be prepared in advance.
- Simple, understated decoration that still looks special enough for birthdays and celebrations.
Grocery List
- Produce: Optional garnish: fresh berries or mint leaves
- Dairy: Unsalted butter, whole milk, heavy cream, large eggs
- Pantry: All-purpose flour, granulated sugar, cornstarch, baking powder, fine salt, semisweet or dark chocolate, neutral oil (canola or vegetable), pure vanilla extract, light corn syrup (optional)
Full Ingredients
Vanilla Sponge Cake Layers
- 2 1/4 cups (270 g) all-purpose flour
- 2 1/2 tsp baking powder
- 1/2 tsp fine salt
- 1 1/2 cups (300 g) granulated sugar
- 1/2 cup (115 g) unsalted butter, softened to room temperature
- 1/4 cup (60 ml) neutral oil (canola or vegetable)
- 4 large eggs, at room temperature
- 2 tsp pure vanilla extract
- 1 1/4 cups (300 ml) whole milk, at room temperature
Vanilla Pastry Cream (Custard) Filling
- 2 cups (480 ml) whole milk
- 1/2 cup (120 ml) heavy cream
- 6 large egg yolks
- 2/3 cup (135 g) granulated sugar
- 1/4 cup (30 g) cornstarch
- 1/4 tsp fine salt
- 2 tbsp (28 g) unsalted butter, cut into small pieces
- 2 tsp pure vanilla extract (or 1 vanilla bean, split and seeds scraped)
Chocolate Ganache Glaze
- 8 oz (225 g) semisweet or dark chocolate (about 55–70% cacao), finely chopped
- 3/4 cup (180 ml) heavy cream
- 2 tbsp (28 g) unsalted butter
- 1 tsp light corn syrup (optional, for extra shine)
- Pinch of fine salt
Optional Garnish
- Extra chopped chocolate or chocolate curls
- Fresh berries or mint leaves
- Light dusting of powdered sugar on the serving plates
Step-by-Step Instructions
Step 1: Make the vanilla pastry cream filling
Start with the pastry cream so it has time to chill and thicken. In a medium bowl, whisk together the egg yolks, granulated sugar, cornstarch, and salt until the mixture is smooth, pale, and slightly thickened. Set aside. In a medium saucepan, combine the whole milk and heavy cream. If using a vanilla bean, add the seeds and pod now. Heat over medium until the mixture is steaming and just beginning to bubble around the edges, but not boiling.
Slowly pour about half of the hot milk mixture into the yolk mixture while whisking constantly to temper the eggs. Pour the tempered yolk mixture back into the saucepan with the remaining milk, whisking well. Return the pan to medium heat and cook, whisking constantly, until the pastry cream comes to a full bubble and thickens to a pudding-like consistency, 2–4 minutes. Remove from heat, whisk in the butter and vanilla extract (if not using a bean), and strain through a fine-mesh sieve into a clean bowl. Press a piece of plastic wrap directly onto the surface to prevent a skin forming. Chill in the refrigerator until very cold and firm, at least 2 hours (or up to 24 hours).
Step 2: Prepare the cake pans and preheat the oven
When the pastry cream is nearly chilled, make the cake. Preheat your oven to 350°F (175°C). Grease two 9-inch (23 cm) round cake pans with butter or nonstick spray. Line the bottoms with rounds of parchment paper, then lightly grease the parchment as well. This helps the delicate sponge release cleanly. Lightly dust the sides of the pans with flour, tapping out any excess. Set the pans aside while you mix the batter.
Step 3: Mix the vanilla sponge cake batter
In a medium bowl, whisk together the all-purpose flour, baking powder, and salt. In a large mixing bowl (or the bowl of a stand mixer), beat the softened butter, neutral oil, and granulated sugar on medium-high speed for 3–4 minutes, until very light and fluffy. Scrape down the bowl as needed. Add the eggs one at a time, beating well after each addition, then mix in the vanilla extract.
With the mixer on low speed, add the dry ingredients in three additions, alternating with the milk in two additions (dry–milk–dry–milk–dry). Mix just until the batter is smooth and no dry streaks remain; avoid overmixing so the cake stays tender. If needed, finish folding by hand with a spatula to ensure everything is evenly combined.
Step 4: Bake and cool the cake layers
Divide the batter evenly between the prepared pans (a kitchen scale helps; each pan should have roughly the same amount). Smooth the tops with a spatula. Bake for 24–28 minutes, or until the cakes are lightly golden, spring back when gently pressed, and a toothpick inserted into the center comes out clean or with a few moist crumbs.
Remove the pans from the oven and let the cakes cool in the pans for 10–15 minutes. Run a thin knife around the edges, then invert the cakes onto wire racks, peel off the parchment, and turn them right side up. Allow the layers to cool completely to room temperature before assembling, at least 45–60 minutes. If the tops dome, you can later trim them flat with a long serrated knife for a neater layer cake.
Step 5: Level, fill, and stack the cake
Once the cake layers are cool and the pastry cream is well chilled, you are ready to assemble. If needed, level the tops of the cakes with a serrated knife so the layers are flat and even. Place one cake layer on a serving plate or cake stand, securing it with a small dab of pastry cream underneath to prevent slipping.
Briefly whisk the chilled pastry cream to loosen it into a smooth, spreadable consistency. For the neatest look, transfer it to a piping bag and pipe a thick, even layer over the first cake round, leaving a small 1/4-inch border at the edge so it does not spill out. Alternatively, spread the cream gently with an offset spatula. Carefully place the second cake layer on top, cut side down if leveled, and press very gently to set it. If any cream squishes out, clean up the edges with a spatula. Chill the stacked cake for 20–30 minutes to firm up before you add the ganache.
Step 6: Make the chocolate ganache glaze
Place the finely chopped chocolate in a heatproof bowl. In a small saucepan, heat the heavy cream, butter, corn syrup (if using), and a pinch of salt over medium heat until the cream is steaming and just beginning to simmer around the edges. Do not let it boil vigorously. Pour the hot cream mixture over the chopped chocolate, making sure all the chocolate is submerged. Let it sit undisturbed for 2–3 minutes to melt.
After resting, gently whisk from the center outward until the mixture becomes smooth, glossy, and fully combined. If there are a few unmelted bits, you can warm the bowl briefly over a pot of gently simmering water, stirring constantly, just until melted. Let the ganache cool at room temperature, stirring occasionally, until it thickens to a pourable but not runny consistency, about 15–25 minutes. It should ribbon off a spoon and slowly smooth back into itself.
Step 7: Glaze the cake and serve
Place the chilled, filled cake on a wire rack set over a baking sheet, or leave it on the cake stand if you are confident pouring. Starting in the center of the cake, slowly pour the ganache over the top, guiding it gently with an offset spatula toward the edges. Encourage some ganache to drip down the sides for that classic Boston cream look, but try not to completely coat the sides so the layers remain visible.
If desired, decorate the top with chocolate curls, a few berries, or a small ring of whipped cream once the ganache has begun to set slightly. Transfer the cake to the refrigerator and chill for at least 30 minutes to set the ganache and firm the layers before slicing. For the best texture and flavor, let the cake sit at cool room temperature for 20–30 minutes before serving. Slice with a sharp knife, wiping the blade between cuts for clean layers.
Pro Tips
- Make the pastry cream a day ahead so it is fully chilled and thick; this makes assembly much easier and prevents the filling from squishing out.
- Use room-temperature eggs and milk for the cake batter to help it mix evenly and rise higher.
- For extra moist cake, you can brush the cooled layers with a light simple syrup (equal parts sugar and water, simmered and cooled) before adding the pastry cream.
- Adjust ganache thickness by temperature: if it is too runny, let it cool longer; if too thick, warm it briefly over gentle heat or in a microwave in a few short bursts.
- Chill the assembled cake briefly before pouring the ganache; a cool surface encourages pretty drips rather than a full slide of chocolate down the sides.
Variations
- Extra-vanilla version: Add the seeds of an additional vanilla bean to the pastry cream and increase the vanilla in the cake batter to 3 tsp for a more pronounced vanilla flavor.
- Coffee-chocolate twist: Stir 1–2 tsp instant espresso powder into the hot cream for the ganache to give the chocolate topping a subtle mocha note.
- Mini Boston cream cakes: Bake the batter in 24 cupcake wells (lined) and fill each cupcake with pastry cream, then spoon ganache over the tops for individual servings.
Storage & Make-Ahead
Because of the pastry cream, this cake should be stored in the refrigerator. Cover the cake loosely with plastic wrap or keep it in a covered cake keeper. It will keep well for 2–3 days; the sponge may soften slightly over time as it absorbs some of the custard, which many people enjoy. For the best flavor and texture, bring slices to room temperature for about 20–30 minutes before serving.
To work ahead, you can make the pastry cream up to 24 hours in advance and store it refrigerated with plastic wrap pressed directly onto the surface. The cake layers can be baked, cooled, wrapped tightly in plastic, and stored at room temperature for up to 1 day, or frozen for up to 1 month (thaw in the fridge overnight before assembling). Make the ganache just before you are ready to glaze so it has the right consistency.
Nutrition (per serving)
Approximate values per serving (1 of 12): about 560 calories; 8 g protein; 63 g carbohydrates; 32 g fat; 19 g saturated fat; 175 mg cholesterol; 260 mg sodium; 1 g fiber; 42 g sugars. Actual values will vary based on specific ingredients and portion sizes.
