Soak gelatin in a bowl of cold water until softened, about 10 minutes. In a saucepan, heat cream with sugar. Squeeze gelatin well and add to hot cream. Stir until dissolved. Stir in yogurt and set about 1/3 of the mixture aside. Let cool, stirring occasionally.
Stir mint liqueur into the larger amount of yogurt mixture until the desired color is achieved. Pour half of the mixture into a pudding mold and freeze until solid. Keep remaining amount slightly warm. Once mixture is solid, top with the plain mixture and chill.
Let remaining yogurt mixture cool. Once the second layer is solid, pour remaining yogurt cream on top. For best results, refrigerate overnight. Invert mint-yogurt on a platter and serve for dessert.