Warm butter in a large, heavy-bottomed saucepan over medium high heat. Add onions and cook for two minutes, stirring frequently. Add the garlic and continue to cook and stir until softened (about another 3 minutes). Add crushed red pepper, curry powder, coriander and cayenne pepper. Continue stirring and cooking until spices become very fragrant (1 – 2 minutes).

Add canned pumpkin and chicken broth, stirring to combine. Bring mixture to a boil, reduce heat and simmer for 15 minutes, stirring occasionally.

While the soup is cooking, assemble the Toasted Cumin Crema. Place the whole cumin seeds in a small sauté pan over medium heat. Toast until fragrant and lightly golden. Swirl the seeds around in the pan every few minutes to keep them from burning on one side. Place the toasted cumin seeds in a spice grinder or mortar and pestle and grind until coarse. Stir into the sour cream and season with salt and pepper to taste.

After 15 minutes, blend the soup until smooth. I used an immersion blender to do this; however, you could also use a regular blender. Simply transfer the soup (in several batches) to a blender, cover tightly* and blend until smooth. If using a regular blender, return the soup back to the saucepan over low heat.

Add brown sugar, stirring to combine. Slowly stream in milk and heavy cream, stirring until completely incorporated. Taste your soup and adjust seasonings to taste. I added about a teaspoon and a half of kosher salt. If you find the soup is not spicy enough, you can add a bit more cayenne pepper (or some of the other spices). If the soup is too spicy, you can add more heavy cream.

To serve, ladle the soup into a small bowl and spoon in a dollop of crema.