Fill a large pot 2/3 full with water and place over high heat. Once boiling, add a few generous pinches of salt and add the pasta. Cook according to the time on the package until al dente. Drain and return to pan (off heat). Set aside.
While the pasta is cooking, fill another large pot 2/3 full with water and place over high heat. Add the squash and sweet potatoes. Bring to a boil and cook until the veggies are fork-tender, 7-8 minutes. Drain and blend.
Place a medium sauté pan over medium heat. When hot, add the olive oil. Dice and add 1 small onion and cook until soft, about 5m. Add 1 clove garlic, minced, and stir for another minute. Add:
Stir. Remove from heat. Pour in the vegetable broth and stir to release any of the browned bits of onion and spices. Pour into blender pitcher.
Add coconut milk, 2 tbsp nutritional yeast (if using) and 1 tsp soy sauce. Puree until completely smooth. Taste and add additional soy sauce, a teaspoon at a time, to taste, along with more salt and pepper if desired.
Pour sauce over cooked pasta in the pan. This recipe makes a lot of sauce (because I like it saucy!) so you might not want to use it all. Stir gently with a wooden spoon until all of the pasta is coated. Serve.
Modified from Kitchen Treaty