Instant Pot Butternut Squash Soup

Name: Instant Pot Butternut Squash Soup
Ingredients: 5 ounces pancetta, cut into 1/2-inch pieces; 2 medium carrots, cut into 1-inch pieces; 1 stalk celery, cut into 1-inch pieces; 1/2 medium onion, cut into 1-inch pieces; 4 large sage leaves, minced; 1/2 teaspoon ground cumin; Kosher salt and freshly ground black pepper; 7 cups butternut squash cut into 1-inch pieces (from a 2-pound squash); 3 cups chicken stock; 1 cup cream, optional; 8 ounces small white button mushrooms, stems trimmed, cut into 1/8-inch slices; Pinch ground cumin; Kosher salt; Creme fraiche or full-fat Greek yogurt, thinned to a pourable consistency with 1 to 2 tablespoons water; Minced chives