Polenta Lasagna

Ingredients (15)

• 1 tablespoon olive oil
• 1/2 yellow onion, diced
• 1 red bell pepper, diced
• 8 oz mushrooms, sliced
• 4 cups packed spinach
• 4 garlic cloves, minced
• 1 cup ricotta cheese
• 1 large egg
• 1/2 teaspoon dried basil
• 1/4 teaspoon dried oregano
• 18 oz tube polenta
• 24 oz marinara sauce
• 2 cups shredded mozzarella cheese, divided
• 1/2 cup shredded Parmesan cheese
• Garnish: freshly chopped basil and crushed red pepper flakes