Chocolate and lime go so well together. You can also make a lemon icing if you prefer, replacing the lime with a large lemon.
For the cake
- 175g (6oz) butter
- 175g (6oz) soft dark brown sugar
- 3 free-range eggs
- 135g (4¾oz) self raising flour
- 4 tbsp cocoa powder
For the candied lime rind
- Grated rind of 3 limes
- 50g (1¾oz) caster sugar
- 4 tbsp water
For the buttercream
- 100g (3½oz) unsalted butter, slightly softened
- 200g (7oz) icing sugar
- grated rind of 3 limes, plus extra to decorate, and the juice of 2–3 (depending on the size of the limes – you need enough juice to make a soft, spreadable icing)
- dark chocolate, roughly chopped, to decorate
- Preheat the oven to 200ºC/fan 180ºC/gas mark 6. Beat the butter and sugar together until pale and fluffy. Add the eggs one at a time, beating well between each addition. Fold in the flour and cocoa powder. If the mixture is very stiff, stir in a tablespoon of milk (or rum!). Pour into a greased and lined 20cm (8in) diameter, 2cm (¾in) deep cake tin and bake for 35–40 minutes or until a skewer inserted into the centre comes out clean and the cake is puffed up and golden. Turn the cake out on to a wire rack and leave to cool.
- Meanwhile, make the candied lime rind. Place the caster sugar and water into a small saucepan and stir until the sugar dissolves. Add the lime rind and cook over a medium heat for 10 minutes or until the sugar syrup has reduced and the lime rind is soft and looks a little like marmalade. Sprinkle the lime rind over a baking sheet lined with non-stick baking paper and leave to cool and harden.
- To make the icing, beat the butter and icing sugar together, using an electric mixer or by hand (start off gently or the icing sugar will fly everywhere), until pale and light, but don’t let it get too fluffy – you want a fairly solid buttercream for this cake. Add the lime juice and rind and beat again. Chill in the refrigerator until the buttercream is firm but still spreadable.
- Spread the buttercream over the top of the cake using a palette knife. Decorate with the candied lime rind and dark chocolate.