Preheat oven to 400F.
Spread cubed squash on two baking sheets, drizzle cubes with 2 tablespoons olive oil. Season with salt & pepper.
Roast 15 minutes, stir squash, and roast for about 10 minutes longer.
Meanwhile, heat sour cream and dried sage in small saucepan over medium heat until small bubbles begin to form around edges of pan. Remove from heat and let steep 15 minutes.
Melt butter in large pot on medium heat. Add shallots, and saute until translucent and beginning to soften, stirring often, 3-4 minutes.
Add roasted squash, then broth.
Increase heat and bring to boil, then reduce to medium, cover pot, and simmer until vegetables are very tender, stirring occasionally about 10 minutes.
Let cool about 15 minutes.
In batches, puree soup in processor until smooth. Return to pot, whisk 1 cup sage cream into soup, season to taste with salt & pepper.
Serve with with fresh sage cream, shredded cheese and a leaf of sage.