Preheat over to 400 degrees.
Toss butternut squash and onion with garlic and olive oil. Spread in a single layer on a foil-lined baking sheet and season to taste with salt and pepper. Roast in oven for 25 to 30 minutes.
Combine squash and chicken broth in blender and puree on high speed until well blended. Stir in half and half. Serve hot.