1. Preheat oven to 375°F. To make the filling, place thawed spinach in a colander in the sink or over a deep bowl. Using your hands, squeeze or press spinach vigorously to remove excess liquid. Continue to squeeze and press spinach until it is almost dry; excess liquid left in the spinach will make a soggy lasagna. Once drained, you should have about 3 cups spinach. Set aside.

2. Working in batches as necessary, place mushrooms into a food processor fitted with a metal blade. Pulse 6-8 times, until mushrooms are finely diced but not puréed. Place diced mushrooms in a bowl. Repeat with remaining mushrooms until all mushrooms are diced.

3. In a large sauté pan over medium heat, sauté diced mushrooms with 1/8 teaspoon of salt and pepper, stirring occasionally, until the mushrooms release their liquid and liquid evaporates, 15-20 minutes.

4. In a medium bowl, combine mushrooms, drained spinach, roasted garlic purée, tofu, nutritional yeast, basil, oregano, remaining 1/8 teaspoon salt and cayenne, if using. Season to taste with more basil, oregano, and/or cayenne as needed.

5. In a 5- to 6-quart pot over high heat, bring 4 quarts of water to a boil. When water is boiling, add lasagna noodles one at a time, criss-crossing the layers of noodles so they don’t stick.

6. Turn off heat and let noodles soften in hot water for 6 minutes (They will seem undercooked.) Drain. If you need to hold the noodles before assembly, return noodles to pot and cover with cold water. Drain and pat dry thoroughly before using.

7. To assemble the lasagna, spread 1 cup of marinara sauce over the bottom of a 9 1/2x13x2-inch baking pan. Cover sauce with 3 to 4 noodles. Spread 1/4 (about 2 cups) of the spinach-tofu filling over the noodles.

8. Repeat 3 times, using the same amounts of sauce, noodles, and filling each time. Top finished lasagna with 1 cup of marinara sauce. Any remaining marinara sauce can be spooned over the lasagna at serving time, or reserved for another use.

9. Place lasagna on middle rack of the oven and bake, uncovered, for 40 minutes. Cover lasagna with foil and bake for an additional 20 minutes.

10. Remove from oven and discard foil. Let lasagna rest for 10 minutes before serving. While lasagna is resting, reheat remaining marinara sauce, if desired. Cut into squares with a serrated knife. Serve with extra warmed marinara sauce and garnish each serving with chopped parsley, if desired.