Butternut squash and sweet potatoes combine perfectly in this pureed soup.
Melt butter in a large pot over medium-high heat. Add butternut squash, sweet potato, onion, carrot, celery, and garlic; cook and stir until lightly browned, about 5 minutes.
Stir in chicken stock and bell peppers; bring to a boil. Reduce heat to low, cover, and simmer until squash and potato tender, about 40 minutes.
Fill a blender halfway with soup. Cover and hold lid down with a potholder; pulse a few times before leaving on to blend. Pour into a pot. Repeat with remaining soup. Season with salt and black pepper.