Pre-heat oven to 375 F (191 C).
In a medium-heat skillet, saute onions until translucent. Add garlic and saute for another 3 - 5 minutes, stirring regularly to avoid burning.
Peal and thinly slice your sweet potatoes (I used a mandolin - be very careful if you do this).
In a blender, blend the cooked onion/garlic, milk, nutritional yeast, tofu, and all the spices until smooth and creamy.
In a medium-heat skillet, saute the mushrooms and spinach; you want to get most of the moisture out of it.
In a casserole dish, spread a thin layer of our sauce.
Then layer as follows:
Sweet Potatoes
Sauce
Mushroom/spinach
Cheese
Sweet Potatoes
Sauce
Mushroom/spinach
Cheese
Sweet Potatoes
Sauce
Mushroom/spinach
Cheese
Sweet Potatoes
Sauce
Cook for 45minutes.
Take out, add remaining shredded cheese on top and cook for an additional 15 - 20 minutes. This will keep the cheese from drying out.
You will know this dish is done when sweet potatoes are fork-tender.