The natural sweetness of this vegetarian honeynut squash soup is amplified with honey and vegetable broth. Sage flavors the soup and sour cream brings in a little tang, balancing the earthy flavors.
Melt butter in a large Dutch oven over medium-high heat, stirring occasionally, until brown and nutty-smelling, 4 to 5 minutes. Reduce heat to medium; add onion and stir to coat. Cook, stirring occasionally, until softened, about 8 minutes, adding garlic and sage during the last 2 minutes of cooking time. Add squash and broth; increase heat to high and bring to a boil. Reduce heat to medium and simmer, stirring occasionally, until the squash is very tender, 30 to 35 minutes.
Transfer half of the squash mixture to a blender; add 2 tablespoons sour cream. Secure the lid on the blender; remove the center piece of the lid to allow steam to escape. Cover the opening with a kitchen towel. Process until smooth, about 30 seconds. (Use caution when blending hot liquids.) Transfer the mixture to a bowl. Repeat with the remaining squash mixture and 2 tablespoons sour cream. Return all of the pureed soup to the pot. Stir in honey, cayenne, nutmeg and salt.
Combine water and the remaining 1 tablespoon sour cream in a small bowl; stir until well-blended.
Divide the soup evenly among 4 bowls and drizzle with the sour cream mixture.
Refrigerate in an airtight container for up to 5 days or freeze for up to 2 months.