1. In a soup pot or Dutch oven heat oil over medium heat. Add onion and saute until softened, about 5 minutes. Add curry paste, garlic, ginger, and lemongrass and saute until the paste is fragrant and starting to brown, about 2 minutes.
2. Stir in stock or broth and pumpkin. Reserve a generous spoonful of the solidified coconut milk at the top of the can, then add the remaining can contents to the pot along with monk fruit and salt.
3. Bring to a simmer, then cover, reduce heat to low, and simmer for 10 minutes to allow flavors to meld. Use a hand blender or countertop blender to puree the soup.
4. To serve, ladle soup into bowls. Drizzle with a little of the reserved coconut milk and garnish with chiles and cilantro.