• Preheat oven to 375 degrees Fahrenheit. While oven is preheating, prepare lasagna.

Vegetables

• In a sauté pan over medium heat, add olive oil. Add diced onion and cook for about 3-4 minutes, or until edges begin to brown and onions begin to turn translucent. Add garlic and cook an additional 30 seconds. Add diced zucchini and mushrooms and cook another 3-4 minutes, or until veggies have softened slightly. Add spinach and stir until wilted, about a minute. Remove from heat and set aside.

Bechamel sauce

• Meanwhile, in a saucepan over medium heat, melt butter. Add flour and whisk to create a paste. Cook for 1 minute, then whisk in whole milk. Add salt, pepper, Italian seasoning, and nutmeg and continue whisking until mixture comes to a simmer. Reduce heat to medium-low and cook until sauce thickens, stirring frequently, about 4 to 5 minutes. Remove from heat.

Lasagna layering

• Lightly grease a 9x13 casserole dish. Add a small amount (½ cup or less) of your bechamel sauce to the bottom of the dish and spread into a thin layer.
• Add 3 to 4 lasagna noodles (depending on size and shape) to the bottom of the pan. Top with half of the sauteed vegetables and spread into an even layer. Top with ⅓ of the remaining bechamel sauce and ⅓ of your shredded cheeses. Repeat this step once more, adding another layer of noodles, vegetables, sauce, and cheeses.
• Add a third layer of lasagna noodles, then top with remaining bechamel sauce and remaining shredded cheeses. Make sure to cover lasagna noodles completely. Cover casserole dish with foil.
• Bake for 20 minutes on the center rack of the oven, covered. Remove foil and bake for another 20 to 25 minutes, or until cheese is golden brown across the top.
• Remove from oven and allow to rest for 20 minutes before slicing and serving.