Blend spice paste ingredients in a blender or food processor with 2 tablespoons of water until fine.
Heat vegetable oil in a pot and stir fry ground spice paste until fragrant, about 5 minutes.
Add coconut milk, kaffir lime leaves, and asam gelugor (if using).
When sauce comes to a boil, season with salt to taste. Reduce heat to medium low and allow sauce to simmer for 10 minutes.
Add cubed pumpkin and continue to simmer for another 5 minutes, until pumpkin is tender but not mushy.
Add shrimp and cook for another 3 minutes.
If you did not use asam gelugor, stir in lime juice now. Turn off heat and allow curry to sit for 15 minutes before serving.