Preheat the oven to 400 degrees and thoroughly grease a 17"x12" rimmed baking sheet.
Heat the oil in a skillet over medium heat. Add the mushrooms and allow them to cook down for 5 minutes, stirring frequently. Once they release water and it evaporates you'll know they're done. Add the onion, garlic & dry seasonings and cook for a couple more minutes. Pour in the marinara sauce and add the spinach. Toss until the spinach is wilted. Taste and adjust the seasonings as needed. Set aside.
While the veggies are cooking, prepare the tofu ricotta. Set aside.
Bring a large pot of water to a boil and cook the lasagna noodles until al dente. Drain and add back to the empty pot. Add 3/4 of the pesto and toss to coat the lasagna noodles.
To assemble, spread the mushroom mixture out on the bottom of the baking sheet. Top with the lasagna noodles. Add 12 dollops of ricotta on top of the lasagna - so that each piece will get some ricotta. Finish it off with the remaining pesto.
Place in the oven for 30 minutes - the noodles should be cooked through and the ricotta should be bubbly. Remove from the oven and allow to sit for 5 minutes. Top with fresh basil & vegan parmesan, slice and serve.
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Notes
I used no-boil lasagna noodles, but I still par-boiled them to ensure they would cook through in the oven.
I prefer my mushrooms diced in small pieces, but you could also leave them in slices.
I added basil to the tofu ricotta for extra flavor. Not necessary, but delicious.
FOR FREEZING: Prepare the lasagna completely. Do not bake. Cover and place in the freezer. To reheat, thaw overnight in the fridge and bake in a 400 degree oven for 30-45 minutes.