2. Heat 2 teaspoons of olive oil in a nonstick pan over medium-high heat. Add the mushrooms, season with salt, pepper and oregano and cook for two minutes. Add half of the garlic and cook until the mushrooms are browned on the edges. Set the mushrooms aside in a strainer to allow the excess liquid to drain.
3. Wipe the inside of the pan with a paper towel and heat the remaining olive oil in it over medium-high heat. Add the garlic, salt and pepper and cook for 30 seconds. (It's easier to distribute the salt and pepper in the oil before adding the spinach). Add the spinach (with the water that clings to it) and cook until it is just wilted. Set the spinach in a strainer to allow the excess liquid to drain.
4. Preheat the oven to 325°F.
5. In a medium bowl, season the ricotta cheese with salt, pepper and nutmeg.
6. Cover the bottom of a large baking dish that is at least 2 inches deep with a thin coat of tomato sauce. Line the dish with a single layer of lasagna noodles. Spread 1/3 of the ricotta mixture over the noodles and sprinkle with some of the mozzarella cheese. Spread all of the mushrooms over the cheese and sprinkle with a few tablespoons of breadcrumbs. Repeat with another layer of noodles, cheeses, the spinach mixture and breadcrumbs. Continue with another layer of noodles, the remaining ricotta, a sprinkling of mozzarella and the remaining tomato sauce. Finish with a final layer of noodles sprinkled with the remaining mozzarella and breadcrumbs.
7. Cover with foil and bake for 35 minutes. Remove the foil and continue to bake until the top is golden brown, about 5 minutes more. Let stand for at least 15 minutes before cutting into squares and serving.