Grate the zest from the limes, squeeze the juice and mix with the rum.
Beat the butter and sugar until fluffy, add the eggs one by one, and finally stir in the flour, baking powder, chopped mint and lime-rum mixture until a smooth dough is formed.
Pour the batter into jars and bake in a preheated oven at 175 °C for about 30 minutes.
Garnish the still hot cakes with fresh mint and serve.