Ingredients should be at room temperature.
1. Preheat the oven to 160C fan, 180C, 350F, gas mark 4.
2. Line and grease 4 x 23cm (9inch) baking tins (or use silicone liners).
3. Place the sugars and butter in a bowl and beat until light and fluffy, scraping down the sides at least twice.
4. Place the eggs into a bowl, add the vanilla extract and beat well. Slowly add this to the sugar mixture. Do not over beat.
5. Sift the flour and baking powder together, turn the mixer to a low speed then gradually add the flour to the sugar mixture a third at a time until combined.
6. Add the lime zest, mint extract and lime and mint cordial. Turn the mixer off when they are fully incorporated.
7. Evenly share the mixture between the baking tins and bake for 35-38 minutes. The cakes are baked when they are lightly golden.
Whilst the cakes are baking make the rum syrup
1. Place all the ingredients in a small saucepan and once the sugar is dissolved, gradually bring to the boil. Allow to simmer for 5 minutes until thickened slightly. Set aside to infuse.
2. Remove the tins from the oven and place on a cooling rack. Leave for two minutes to cool and remove them from the tins. Pierce each cake evenly with a skewer and drizzle a third of the rum syrup into the holes.
To make the buttercream
1. Place the butter and cream cheese in a mixing bowl and beat on a medium speed for 5 minutes, until light and fluffy.
2. Turn the speed down and gradually add the icing sugar, a tablespoon at a time, leaving a few seconds between each addition. Use a scraper to push the mixture back into the bowl.
3. Add the lime curd, extract and mix at full speed for 5 minutes.
4. Add the lime juice, boiling water, finely chopped mint and cordial. The buttercream should be firm enough to spread and to pipe on easily.
5. At this point taste and add more icing sugar to adjust texture, if needed, and more mint, according to taste.
To assemble
1. Place one of the cakes on a cake board having first placed a little buttercream on the base, to hold the cake firmly on the board. If you have a cake turntable place the cake board onto it.
2. With a pastry brush, brush the rum syrup onto the top of the cake .
3. Using a spatula evenly spread about 3 tablespoons of buttercream onto the cake. Next spread a heaped tablespoon of lime curd over the buttercream. Add the next sponge layer and repeat until the cake is stacked evenly and level.
4. Spread a layer of buttercream evenly around the edges of the stacked cake and also on the top. Use a cake scraper to smooth the top and sides. Place in a fridge to firm for 30 minutes. Remove the cake from the fridge and spread the second layer of butter cream around the sides and top of the cake using a pallet knife or a cake side scraper to give smooth sides.
5. Place the remaining buttercream in piping bag with a 2mm round nozzle. Pipe 12 or 16 domes around the edge of the cake, then sprinkle crushed lime sweets onto the top of the cake and over the buttercream domes. Finally place a sprig of mint onto each buttercream dome.
Sit back, relax and enjoy!
Alternatively, if making a tray bake:
Spread the syrup over the top of the cake whilst still warm and allow to cool in the tray until almost cool before placing on a cooling rack. Once cool spread 2/3 of the buttercream onto the top of the cake. With the remaining cream pipe domes around the edges of the cake , scatter with crushed lime sherberts and sprigs of mint.
To make 12 cupcakes:
If you wish you can make cupcakes with this recipe. Use half the ingredients and place 2.5 oz of mixture in each case and bake for 18-20 minutes. Place in the fridge for 30 minutes before serving.
