Lasagna w/Portabella, Spinach & Ricotta

Lasagna is so easy and I've made my fair shair over the years. The favorites among family and friends: vegetable lasagna that is so good that even my brothers will eat multiple servings of it despite the lack of meat in it. Or the lasagna bolognese that debuted around Christmas eve last year that has since been recreated numerous times for the masses. There are other kinds I've made, like chicken and spinach alfredo lasagna, that are just as good and quite easy. So today's recipe is based on what I have in my fridge - portabella mushrooms, fresh spinach and ricotta.

Cook a box of lasagna noodles as directed on the box. (Or buy the no-cook lasagna noodles.) Meanwhile, chop up the portabella mushrooms and toss in a skillet with olive oil and cook for 5 minutes. Then add in 2 cups of tomato sauce in the pan and let simmer for a few minutes.
Chop up some fresh spinach. In a medium bowl, mix ricotta cheese with the chopped up spinach and one egg. Season with salt and pepper.
Cover the bottom of a 9x13 baking dish with tomato sauce. Put a layer of the lasagna noodles across the bottom. Cover the layer of noodles with the spinach/ricotta mixture. Cover that the mushroom and sauce mixture. Cover with a fresh layer of noodles. Repeat all steps until you run out of the mixture. Cover with final layer of lasagna noodles. Pour remaining sauce over the noodles. Cover with mozzarella cheese.
Cover with foil and bake at 350 for 45 minutes. Take off the foil and bake for another 15 minutes.