Set the instant pot into the sauté mode and allow it to be hot before adding the oil. Once the oil is hot, add chopped garlic, onions, 3 cups of butternut squash, and sage followed by salt and pepper.
Once the veggies look cooked and roasted(5-7 minutes), transfer them to a blender jar.
In the same pot, add pasta, rest 1 cup of the butternut squash, 2 tsp of the onion-garlic-sage mixture, half the nutritional yeast, almond milk, broth, and dry seasonings.
Season with salt and pepper and pressure cook for 4-minutes in the high manual.
While the pasta is cooking, blend the sautéed onion-butternut squash, cashews, nutritional yeast and lemon juice to a smooth puree. Season with salt and pepper and set aside. After the beep, quick-release pressure and open the lid.
Use a spoon to break the cooked butternut squash cubes and mix them well with the pasta.
Add the vegan cheese sauce and mix it really well.
Vegetarians can add cheddar cheese and heavy cream at this point if they want to. Garnish with parsley and serve warm.