Baked Polenta Lasagna with Spinach and Mozzarella

Why You’ll Love This Recipe

• All the cozy “lasagna” comfort without boiling noodles—quick-cook polenta sets into sturdy, sliceable layers.
• Budget-friendly pantry heroes (jarred marinara and frozen spinach) taste restaurant-ready baked under melty mozzarella.
• Easy to make ahead, slice, and reheat—perfect for weeknights or meal prep.
• Naturally gluten-free and endlessly adaptable to your favorite add-ins.

Grocery List

• Produce: 2 garlic cloves, fresh basil or parsley
• Dairy: Milk (optional), unsalted butter, low-moisture mozzarella, Parmesan
• Pantry: Quick-cook polenta, marinara sauce, frozen chopped spinach, olive oil, kosher salt, black pepper, crushed red pepper flakes, ground nutmeg, parchment paper

Full Ingredients

Polenta Sheet

• 5 cups water
• 1 cup milk (whole or 2%; or sub 1 cup water)
• 1 1/2 cups quick-cook (instant) polenta
• 2 tbsp unsalted butter
• 1 tsp kosher salt, plus more to taste
• 1/2 tsp freshly ground black pepper
• 1 cup finely grated Parmesan cheese

Spinach Layer

• 16 oz frozen chopped spinach, thawed and squeezed very dry
• 1 tbsp extra-virgin olive oil
• 2 cloves garlic, minced
• 1/4 tsp crushed red pepper flakes
• 1/8 tsp ground nutmeg
• Pinch kosher salt

To Assemble & Finish

• 3 cups marinara sauce
• 12 oz low-moisture mozzarella, shredded (about 3 cups)
• 1/2 cup finely grated Parmesan
• Olive oil or nonstick spray, for the baking dish
• Fresh basil or parsley, chopped, for garnish

Step-by-Step Instructions

Step 1: Line the pan and heat the liquids

Line a 9×13-inch baking dish with a parchment sling, leaving overhang for easy lifting. In a medium pot, bring 5 cups water and 1 cup milk to a gentle simmer over medium heat.

Step 2: Whisk in the polenta

Rain in 1 1/2 cups quick-cook polenta while whisking constantly to avoid lumps. Reduce heat to medium-low and continue whisking until thick and bubbling, 3 to 5 minutes. Stir in 2 tbsp butter, 1 tsp kosher salt, 1/2 tsp black pepper, and 1 cup Parmesan. Taste and adjust seasoning.

Step 3: Set the polenta

Scrape the hot polenta into the lined dish and spread to an even 3/4-inch thickness. Smooth the top. Refrigerate until firm, 20 to 30 minutes (30 minutes yields the cleanest slices). Meanwhile, preheat the oven to 400°F.

Step 4: Mix the spinach layer

In a bowl, combine the well-squeezed spinach, 1 tbsp olive oil, minced garlic, crushed red pepper flakes, nutmeg, and a pinch of salt. Fluff with a fork to distribute evenly.

Step 5: Cut the polenta

Use the parchment to lift the polenta slab onto a cutting board. Cut into 12 rectangles (3 rows by 4 columns). Lightly oil or spray the 9×13-inch baking dish (you can reuse the same dish—remove parchment first).

Step 6: Layer like lasagna

Spread 1 cup marinara over the bottom of the dish. Arrange half of the polenta pieces in a snug single layer. Scatter half the spinach over the polenta, then sprinkle with half the mozzarella. Add another 1 to 1 1/2 cups marinara (spooning to cover). Top with the remaining polenta, the rest of the spinach, and the remaining mozzarella. Spoon any remaining marinara over dry spots and finish with 1/2 cup Parmesan.

Step 7: Bake, rest, and serve

Bake at 400°F until the sauce is bubbling around the edges and the cheese is melted, 25 to 30 minutes. For extra color, broil 1 to 3 minutes, watching closely. Let rest 10 minutes to set. Cut into hearty squares, garnish with chopped basil or parsley, and serve hot.

Pro Tips

• Whisk constantly when adding polenta to prevent lumps; add it in a slow, steady stream.
• Season the polenta boldly—its flavor softens once layered with sauce and spinach.
• Squeeze spinach extremely dry; excess moisture can make the bake watery.
• Let the finished casserole rest 10 minutes; cleaner slices and better layers.
• Broil briefly for a burnished, bubbly cheese top—just don’t walk away.

Variations

• Sausage & fennel: Brown 8 oz Italian sausage with a pinch of fennel seeds; scatter between layers with the spinach.
• Mushroom & thyme: Sauté 12 oz sliced cremini with thyme and a splash of balsamic; layer with the marinara.
• White bake: Swap marinara for 3 cups light béchamel or Alfredo; add lemon zest to the spinach and extra nutmeg.

Storage & Make-Ahead

Polenta sheet can be made up to 2 days ahead; wrap and refrigerate. Assemble the casserole up to 24 hours in advance; cover and chill, then bake 30–35 minutes (add a few minutes for the cold start). Leftovers keep 4 days refrigerated. Reheat covered at 350°F for 20 minutes or microwave individual squares. Freeze squares up to 2 months; thaw overnight and reheat at 350°F until hot.

Nutrition (per serving)

Approximate for 1 of 8 servings: 430 calories; 23 g protein; 18 g fat; 35 g carbohydrates; 4 g fiber; 1,200 mg sodium. Values will vary based on marinara and cheese brands.