"This soup is a great-tasting comfort food to take the chill off a cool fall or winter day. Roast the pumpkin on your grill or in the oven. Either way, using the pumpkin shells as bowls adds a fun touch. Sprinkle more nutmeg and pepper over soup before serving."
Spray inside and outside of pumpkin with cooking spray.
Preheat an outdoor grill for high heat and lightly oil the grate.
Place pumpkin, pulp-side down, on the grate. Close the lid. Grill until tender, 15 to 20 minutes. Turn over, skin-side down; grill until pulp is very soft and lightly charred, 20 to 30 minutes. Reduce heat as necessary to keep the grill temperature below 450 degrees F (232 degrees C). Let pumpkin cool on the grill.
Melt butter in a large pot over medium-high heat. Add onions; saute until translucent and lightly browned, about 5 minutes. Add vegetable stock, cornstarch, and curry powder; bring to a boil. Cook and stir until thick and foamy and cornstarch is dissolved, 1 to 2 minutes. Reduce heat to medium.
Scoop pulp out of the pumpkin, reserving the hard shell to use as bowl. Add pulp to the stock mixture, breaking up any large lumps. Stir in milk, sour cream, soy sauce, and sugar. Blend soup with an immersion blender until smooth. Stir in nutmeg, salt, and pepper.
Reduce heat to medium-low. Cook, stirring constantly, until just starting to boil, 5 to 7 minutes. Remove from heat. Serve in the pumpkin shells.
The pumpkin can be roasted in an oven at 450 degrees F (232 degrees C) instead of grilled, if desired. To do this, place the cleaned pumpkin halves, sprayed on both sides with cooking spray, pulp-side-down on a baking sheet and roast for 20 to 30 minutes. Turn over and continue roasting with the pulp-side-up until tender and just starting to char, 20 to 30 minutes more.
Use gluten-free vegetable stock and tamari to make the soup gluten-free.
When pureeing with an immersion blender, take care to not spray or splash the soup by tilting the pot and placing the blender deep in the corner.