1. Take the butternut squash, trim off the top and bottom, split it in half, and then split it down the middle. Put them on a plate and cover it with plastic wrap. Microwave on high until tender (about 8 to 12 minutes). Take it out and let it cool on paper towels. Once it is cool enough to handle, peel off the skin. Should be about 4 cups.
2. Melt the butter in a large pot, and cook the onion, carrot, potato, squash and garlic 5 minutes, or until lightly browned. Pour in enough of the chicken stock to cover vegetables. Bring to a boil. Reduce heat to low, add half and half, nutmeg and cayenne powder. Cover pot and simmer 40 minutes or until all vegetables are tender.
3. Transfer the soup to a blender or use an emersion hand blender to blend until smooth. Return to pot and mix in any remaining stock to attain desired consistency. Season with salt and pepper. Top with Parmigiano-Reggiano