Melt butter in large saucepan over medium-high heat. Add squash, carrot and onion. Sauté for 12 minutes. Add broth and bring to a boil. Cover, reduce heat and simmer for 30 minutes. Remove from heat and stir in half and half, nutmeg and salt.
Place squash mixture in to a blender. Remove center piece of blender lid to allow steam to escape. Place clean towel over opening to avoid splatters. Blend until smooth.