In a large saucepan or wok, heat some oil over medium heat. Add the red curry paste and cook for 1-2 minutes, stirring constantly to release its flavors.
Pour in the coconut milk and chicken or vegetable broth. Stir well to combine and bring to a simmer.
Add the pumpkin, red bell pepper, and onion to the saucepan. Stir and let simmer for 10 minutes to partially cook the pumpkin.
Add the prawns to the saucepan and cook for 5 minutes, or until they are cooked through and turn pink
Stir in the fish sauce, brown sugar, and torn kaffir lime leaves (if using). Cook for an additional 2 minutes.
Add the diced mango to the saucepan and gently stir to combine. Cook for another 2 minutes.
Remove from heat and garnish with fresh coriander leaves.
Serve over steamed jasmine rice, with lime wedges on the side for squeezing over the dish. Enjoy!