Bring a large pot of lightly salted water to a boil. Cook macaroni in the boiling water, stirring occasionally, until tender yet firm to the bite, about 8 minutes. Drain and place macaroni in a casserole dish.
Place 2 cups chopped buttercup squash and acorn squash in a microwave-safe bowl. Microwave until tender, about 90 seconds. Transfer to the casserole dish. Repeat with the remaining portions of chopped squash. Add 3/4 of the chopped onion, Fresno chiles, and green chiles; mix well. Sprinkle bread evenly on top of the vegetables.
Place the remaining chopped onion, beans, soy milk, vegetable stock, mushrooms, lemon, tahini, olive oil, miso paste, nutritional yeast, chile powder, sage, and cayenne pepper in a blender. Blend until creamy. Pour sauce over the bread and vegetables until thoroughly doused. Season with black pepper.
Bake in the preheated oven until lightly browned and bubbling, 35 to 40 minutes.
For milder spice level, substitute fresno peppers with red mirasol peppers, green chiles with
Anaheim peppers, and jalapenos with poblano peppers. You can also replace jalapenos with serrano peppers (hot!) if you're feeling adventurous. Just remember to put on gloves before dicing.
Substitute white miso paste with a darker miso if a saltier taste is desired.
You can use any canned white bean in place of cannellini beans.
Substitute soy milk with any dairy-free milk you prefer.
Due to immense variation is squash sizes, if the vegetables don't seem well coated in sauce, feel free to pour as much extra vegetable stock or soy milk as needed evenly on top of casserole.