In a pot, melt the butter and add the butternut squash, potatoes, and salt and black pepper. Saute for a few minutes. Add the vegetable broth, and cook on high heat for about 5 minutes, or until the potatoes and squash are fork tender.
With a hand blender, puree the squash mixture to the desired consistency, and cook on medium heat for 5 minutes. Add the heavy cream and cook for an additional minute.
Remove the soup from the heat. Finish with the freshly grated Parmigiano cheese, and a drizzle of truffle oil. Serve immediately.