Preparation

• Thaw frozen spinach and squeeze out excess liquid.
• Cook lasagna noodles until al dente. Drain, rinse under cold water and lay flat on a few sheets of parchment paper.
• In a large nonstick skillet over medium-high heat, melt the butter. Add in the onions, salt and pepper. Saute for 2-3 minutes.
• Add in garlic and cook for an additional minute. Then add in the chopped mushrooms and Italian seasoning.
• Cook until mushrooms have cooked down and liquid has evaporated, about 7-10 minutes. Remove from heat and stir in drained spinach and more salt and pepper.
• In a bowl, combine ricotta, Parmesan cheese, half of the mozzarella, eggs, and parsley. Add the spinach mixture and combine.
• In a heavy-bottomed saucepan, melt butter over medium heat. Add flour and whisk to make a roux.
• Slowly pour in milk, whisking continually until thickened. Stir in Parmesan cheese, nutmeg, salt, and pepper.
• Preheat the oven to 375°F.
• Pour about ½ cup white sauce in the bottom of a 9x13-inch oven-safe pan.
• Layer lasagna noodles, spinach mixture, and white sauce, repeating two more times.
• Top with final noodles, last of the white sauce, and remaining mozzarella cheese.
• Cover with greased foil and bake for 30 minutes. Remove foil and bake for an additional 10 minutes.
• Cool for at least 15 minutes prior to serving.