Heat a 4-5 quart saucepan over medium-high heat. Toss in the onion and sauté it until it begins to brown, about 5 minutes, adding a splash of water if it begins to stick.
Add the mushrooms and cook, stirring, until they begin to exude liquid. Add the garlic and cook, stirring, for another minute or two.
Stir in the tomatoes and broth. Drain the beans and measure out ½ cup of them. Set these aside and add the rest of the beans to the pot.
Add the next 6 ingredients, basil through pepper flakes. Bring to a boil, reduce the heat to low, and cover. Simmer for 15 minutes.
Add the lasagna pieces and zucchini, and adjust the heat to a slow boil. Cook uncovered until the lasagna is al dente (check the lasagna package for time).
Meanwhile, place the ½ cup beans in a blender with ½ cup plant milk and 2 tablespoons nutritional yeast. Blend until smooth.
When the noodles are cooked, stir in the blended beans and the spinach. Check the soup and if it needs more liquid, add more broth or water.
Check the seasoning and add salt and additional herbs as needed.
Remove from the heat, cover, and let stand a few minutes until the spinach has wilted. Serve now or allow to rest while the flavors combine.
