Cupcakes: Preheat the oven to 180 degrees C and prepare a cupcake tray with patty cups.
In a bowl mix the buttermilk, rum and vanilla essence. Set aside. In another bowl mix the flour, baking powder and salt. Set aside.
In the bowl of your food processor quickly whisk the butter and sugar until white. Reduce speed and add the eggs one at a time scraping the sides of bowl after each egg.
Stir in the dry ingredients and the liquid ingredients in the following order: 1/3 of the dry ingredients; 1/2 of the buttermilk; 1/3 of the dry ingredients; remaining butter milk and the remaining dry ingredients.
Scrape the sides of the bowl and double check that the dry ingredients have been added. Pour this batter into the patty cups and fill only half way. Bake in the oven for 20 minutes.
Once cooked remove from the oven and cool for 5 minutes. Meanwhile, prepare the syrup.
Syrup: In a small saucepan bring the water and sugar to the boil. Once the sugar is dissolved remove from heat and stir in the rum.
Add the lime zest and mint then brew for 5 minutes.
Icing: Using your food processor whip the cream cheese and butter at high speed until creamy. Reduce speed then add the icing sugar and whisk for 1 minute until smooth.
Whisk 2 minutes at high speed and then stop, scrape the sides of the bowl and add the rum and lime zest. Whisk one last time at medium speed.
Assembly: Cut the top of each warm cupcake and set aside. Pour the syrup over the cupcakes then put the tops back in place and cool.
Top the cooled syrup soaked cupcakes with the icing. Add a slice of lime and a few fresh mint leaves.