Sweet pumpkin, smoky chiles, and tangy buttermilk make this a great cold-weather soup. Be creative with substituting other spices (cinnamon, ginger, cloves, cumin, etc.) to change the feel of the soup. It’s great hot or cold with a bit of creme fraiche.
Preheat oven to 425 degrees F (220 degrees C).
Bake the pumpkin on a baking sheet in the preheated oven until soft, 30 to 40 minutes.
Combine 2 cups chicken broth and chile peppers in a saucepan over medium-low heat; simmer for 30 minutes.
Melt butter in a large stockpot over medium heat. Cook and stir onion in the butter until caramelized, about 45 minutes. Transfer to a bowl.
Cook leeks in the same stockpot until tender, 10 to 15 minutes. Add pumpkin, chicken broth with chile peppers, caramelized onion, remaining 3 cups chicken broth, and cumin. Simmer until flavors combine, about 5 minutes.
Puree soup with an immersion blender until smooth. Add bay leaf, salt, and pepper. Remove from heat; stir in buttermilk. Discard bay leaf before serving.
Per Serving: 209 calories; protein 7.5g; carbohydrates 44.3g; fat 2.3g; cholesterol 7.6mg; sodium 908.5mg.