In a saucepan, combine 350 ml milk, 3 teaspoons sugar, and 2 tablespoons dulce de leche.
Heat on medium heat, stirring constantly for about 5 minutes until steaming hot.
Remove from heat, add 4 teaspoons unsweetened cocoa powder, and stir until the mixture is smooth and lump-free.
Add exactly 3 drops of mint oil (no more), stir once, and let steep for 1 minute.
Stir in 6 cl white rum.
Pour into cups or glasses and top with whipped cream and chocolate flakes.
Alternative method for a more chocolatey drink: In a saucepan, combine 250 ml milk, 100 ml cream, and 70 g chocolate flakes. Heat on medium-low heat, stirring constantly for about 5 minutes until the chocolate is fully melted and the mixture is hot. Remove from heat, add 2 tablespoons dulce de leche, 3 drops mint oil, and 6 cl white rum, stirring well. Pour into cups and top with whipped cream and chocolate flakes.