Preheat oven to 400° and line a baking sheet or cookie sheet with parchment paper.
Place beans, flax egg, nutritional yeast, garlic, salt and cayenne in the food processor. Blend until smooth.
Spread the mixture onto the parchment paper in the shape of a pizza crust, about 1/3 inch thick. You’ll fill most of the width of the baking sheet.
Bake for 20 minutes, then carefully flip the crust to bake on the other side 15-20 minutes. NOTE: To flip, I place another sheet of parchment and another baking sheet over the one the crust has been on, and using oven mitts I flip the sheets together. Then the crust will be on the new baking sheet. Slowly and carefully peel the original parchment off of the crust. Careful not to break :) Bake 5-10 minutes longer.
While the crust bakes, sauté the shiitake mushrooms and onions in a bit of olive oil. If you haven’t already, you can roast the squash now (toss with olive oil, and roast slices for 30 minutes at 350°F)
When the crust is finished, top with the tomato sauce, vegan cheese, greens, squash, mushrooms and onions. Bake for 10 more minutes then serve.