Soak the gelatin sheets in cold water until softened. In a saucepan, combine 40 cl coconut milk and 200 g sugar. Heat gently, stirring with a wooden spoon until the sugar fully dissolves.
Drain the gelatin and stir it into the warm coconut milk mixture until completely melted. Remove from heat, cool to room temperature, then refrigerate until it begins to set (about 30 minutes).
Whip 30 cl heavy cream to soft peaks. Gently fold into the chilled coconut mixture. Pour into a soufflé dish or springform pan. Freeze for 2 hours, then transfer to the refrigerator 1 hour before serving.
For the sauce: Heat 20 cl coconut milk in a saucepan over low heat. Add chopped or grated 200 g white chocolate, stirring until melted. Stir in 10 cl white rum. Pour into a sauceboat and keep warm.
To serve: Unmold the dessert onto a platter, sprinkle with 120 g grated coconut. Garnish with lime slices and drizzle with white chocolate sauce.
