Cheesy Polenta Lasagne with Mushrooms and Seitan

A vegetarian twist on traditional lasagne using creamy polenta layers instead of pasta, filled with savory mushrooms and seitan in a rich cheese sauce made with Fontina and Gruyère.

6 servings

53 min

Published October 4, 2025

Ingredients

•½ stick unsalted butter
•3 tablespoons all-purpose flour
•2½ cups whole milk
•¼ pound Italian Fontina
•3 ounces Gruyère
•½ teaspoon grated nutmeg
•3 cloves garlic
•3 tablespoons olive oil
•10 ounces cremini mushrooms
•8 ounces seitan
•½ teaspoon thyme leaves
•3 tablespoons water
•2 logs ready-made plain polenta

Cooking Instructions

1.
Preheat oven to 425°F with rack in upper third. Lightly butter a 2-to 2 1/2-quart shallow baking dish.
5 min
2.
Melt butter in a 2-to 3-quart heavy saucepan over medium heat. Whisk in flour until smooth, then cook roux, whisking frequently, until pale golden, 2 to 3 minutes.
3 min
3.
Meanwhile, heat milk in a separate small saucepan until just about to boil. Add milk to roux in 2 batches, whisking constantly until very smooth. Bring to a boil, whisking, then cook, whisking, 30 seconds. Remove from heat and whisk in Fontina, half of Gruyère, nutmeg, and 3/4 teaspoon salt. Cover and set aside, whisking occasionally.
10 min
4.
Cook garlic in oil in a 12-inch heavy skillet over medium-high heat, stirring, until beginning to turn pale golden. Stir in mushrooms, 1/2 teaspoon salt, and 1/4 teaspoon pepper and cook, stirring occasionally, until mushrooms are softened, about 3 minutes. Add seitan and thyme and cook, stirring occasionally, until mushrooms and seitan are slightly golden, about 4 minutes. Add water and cook briefly, scraping up any brown bits.
8 min
5.
Spread 1/2 cup cheese sauce in bottom of baking dish.
2 min
6.
Slice 1 log of polenta into 1/4-inch-thick rounds and arrange enough rounds to cover bottom of dish, overlapping slightly. Spoon half of filling evenly over polenta, then spread with half of remaining cheese sauce (about 1 cup). Slice enough rounds from second log to form a second layer. Cover with remaining filling, then cheese sauce. Sprinkle with remaining Gruyère and bake until top is just bubbling and slightly browned, 15 to 20 minutes. Let stand 5 minutes before serving.
25 min

Ingredients

•½ stick unsalted butter

•3 tablespoons all-purpose flour

•2½ cups whole milk

•¼ pound Italian Fontina

•3 ounces Gruyère

•½ teaspoon grated nutmeg

•3 cloves garlic

•3 tablespoons olive oil

•10 ounces cremini mushrooms

•8 ounces seitan

•½ teaspoon thyme leaves

•3 tablespoons water

•2 logs ready-made plain polenta

Cooking Instructions

Preheat oven to 425°F with rack in upper third. Lightly butter a 2-to 2 1/2-quart shallow baking dish.

5 min

Melt butter in a 2-to 3-quart heavy saucepan over medium heat. Whisk in flour until smooth, then cook roux, whisking frequently, until pale golden, 2 to 3 minutes.

3 min

Meanwhile, heat milk in a separate small saucepan until just about to boil. Add milk to roux in 2 batches, whisking constantly until very smooth. Bring to a boil, whisking, then cook, whisking, 30 seconds. Remove from heat and whisk in Fontina, half of Gruyère, nutmeg, and 3/4 teaspoon salt. Cover and set aside, whisking occasionally.

10 min

Cook garlic in oil in a 12-inch heavy skillet over medium-high heat, stirring, until beginning to turn pale golden. Stir in mushrooms, 1/2 teaspoon salt, and 1/4 teaspoon pepper and cook, stirring occasionally, until mushrooms are softened, about 3 minutes. Add seitan and thyme and cook, stirring occasionally, until mushrooms and seitan are slightly golden, about 4 minutes. Add water and cook briefly, scraping up any brown bits.

8 min

Spread 1/2 cup cheese sauce in bottom of baking dish.

2 min

Slice 1 log of polenta into 1/4-inch-thick rounds and arrange enough rounds to cover bottom of dish, overlapping slightly. Spoon half of filling evenly over polenta, then spread with half of remaining cheese sauce (about 1 cup). Slice enough rounds from second log to form a second layer. Cover with remaining filling, then cheese sauce. Sprinkle with remaining Gruyère and bake until top is just bubbling and slightly browned, 15 to 20 minutes. Let stand 5 minutes before serving.

25 min