Carrot Coconut Soup

Name: Carrot-Coconut Soup
Ingredients: ¼ cup (½ stick) unsalted butter; 1 pound carrots, peeled, chopped; 1 medium onion, chopped; Kosher salt and freshly ground black pepper; 2 cups low-sodium chicken broth; 13 .5-oz. can unsweetened coconut milk; 2 tablespoons Thai-style chili sauce plus more for serving; Fresh cilantro leaves (for serving)