Combine roasted squash, water and potato flakes in a blender bowl, and process to a smooth paste. Stir in the flour, a bit at a time, until you end up with a non-sticky dough. Let the dough rest for 30 minutes.
Divide the dough into 6-8 portions. Lightly flour the table or working surface and roll each piece into long sausage shapes about 1 cm (1/2 inch) 1 cm in diameter. Cut each sausage into 2-2.5 cm (1 inch) lengths and roll each piece against the back of a fork. Place the gnocchi on a floured surface or kitchen towel.
Repeat for the rest of the dough.
Bring to a boil 2 liters of salted water and gently dive in the gnocchi.
Wait until they come to the surface of the pan (normally a couple of minutes) and, with a slotted spoon, collect and drain the gnocchi.
For the sauce simply add the fats to a pan (butter + oil) with roughly chopped fresh sage leaves. Cook on medium high heat for 3-4 minutes after it starts bubbling (or until the sage turns slightly crispy).
Add the cooked gnocchi to the piping hot sauce, then pour in the white wine (optional) and allow the alcohol to evaporate for a couple of minutes.
Add a few tablespoons (up to 1/2 cup) of cooking water to the sauce, flick the pan with your wrist to a circular motion to help emulsify the sauce, tossing the gnocchi every now and then. The sauce should turn to creamy and glossy, and evenly coating the gnocchi.
Serve the gnocchi immediately and enjoy with a sprinkle of nutritional yeast or vegan grated cheese if you like.