- Heat the oven to Gas 4, 180°C, 350°F Line a muffintray with paper cases. Whisk together the margarine and sugar until creamy.
- Add eggs and whisk again. Mix in coconut, lime zest and juice. Fold in the flour and baking powder.
- Spoon the mixture into the paper cases and bake for 15-20 minutes. Remove and cool on a baking wire.
- Beat the butter and the icing sugar together with a tablespoon of hot water until smooth. Add a few drops of green colouring and mix until well blended and fluffy.
- Fill a piping bag with a wide nozzle and top each cupcake with a whirl of icing. Decorate with extra lime zest.