Simultaneously you can prepare the onion, mushroom, spinach and pasta sauce (marinara) mix and cook it.
Start layering! In a baking corning ware spary some pam/non-stick spray/oil. Layer the lasanga, the mix, ricotta cheeese. Top off with a layer of marinara sauce and grated cheese (mozzarella/blend).
Bake for 15-20mins and serve!