Heat vegetable oil in a large pot over medium-high heat. Add diced brown onion and minced garlic, cooking for about 2 minutes until softened and fragrant.

Stir in the Thai red curry paste, cooking for an additional 2 minutes to deepen the flavors.

Add the pumpkin or butternut squash chunks, cooking for 2 minutes until well-coated.

Pour in the vegetable stock, remaining coconut milk, and fish sauce. Bring to a simmer and cook for about 8 minutes until the pumpkin is tender.

Use a stick blender to puree the soup until silky smooth. If needed, transfer in batches to a standard blender.

Ladle the soup into bowls and garnish with crispy shallots, red cayenne pepper, and fresh coriander. Optionally serve with warm roti.