Soak sticky rice in hot water for 1 hour, then drain.
Line a steaming basket with cheesecloth, add rice, and steam over boiling water for 25–30 minutes.
Bring 5dl coconut milk, 5 tbsp sugar, pandan leaves, and a pinch of salt to a boil; cover and set aside.
Heat 2dl coconut milk, 2 tbsp sugar, and 1 tsp salt until dissolved for the topping sauce.
Boil split mung beans in water briefly, let sit covered for 15 mins, rinse, dry thoroughly. Fry in a lightly greased pan over high heat until golden-crisp.
Pour the warm 5dl coconut milk mixture over the steamed rice, mix gently, cover for 10 mins, fold again, and rest covered for an additional 20 mins.
Serve rice with fresh mango slices, drizzle with topping sauce, and garnish with crispy mung beans.