Heat the vegan butter or olive oil in a skillet over medium heat. Add the sliced onions and cook until they are beautifully caramelized, about 8-10 minutes.

Stir in the minced garlic, dried thyme, salt, and black pepper. Cook for another minute.

Add the balsamic vinegar or red wine and cook until the liquid reduces slightly, about 2-3 minutes.

Blend the soaked cashews, broth, lemon juice, nutritional yeast, Italian seasoning, miso, and black pepper in a blender until smooth.

Mix in the sliced mushrooms to the skillet and cook until softened, about 5 minutes.

Combine the cashew sauce with the mushroom mixture in the skillet and stir until creamy.

Break the lasagna sheets into irregular pieces and add them to the skillet, followed by the fresh spinach.

Pour in the additional broth or water needed to cook the pasta, about 1-2 cups. Sprinkle with red pepper flakes. Cover and simmer until the pasta is tender, about 10 minutes.