Melt the butter on medium heat in a large frying pan. Saute the onions and butternut squash until they start to brown. Add the mushrooms and garlic; cover and saute for 15 more minutes on low heat. Add the rice and cook for a few minutes uncovered. Add the wine and cook until absorbed. Stir in ½ a ladle of broth at a time (every 5 minutes) until all is used up and rice is creamy but tender. Add more if necessary. Stir well and add the Parmesan cheese. Season with salt and pepper to taste. Sprinkle with parsley before serving.