You will need 2 x 20 centimetre sandwich tins, greased and with the bases line.
1. Preheat the oven to 180°C.
2. For the cake, simply beat the ingredients together until smooth, divide between the two tins – smoothing down the batter – then bake for 18-20 minutes, or until a skewer inserted comes out clean.
For the Filling:
1. Gently bring together the ingredients until smooth, don’t over mix or the mascarpone could split. Set aside until needed.
For the lime curd:
1. Place the lime juice, butter and zest into a pan and bring to the boil.
2. Meanwhile, whisk together the egg yolk and sugar until the sugar has dissolved, then whisk in the cornflour.
3. Pour the boiling lime juice onto the egg mixture and whisk to mix, then pour it back into the pan and over a medium heat whisk it constantly until the mixture thickens and boils.
4. Decant onto a plate, cover it with cling film and allow it to cool completely.
5. To assemble, spread a generous amount of lime curd over one cake (you will have lime curd left over, so keep some in a jar).
6. Pipe the mascarpone in a spiral on top, then top with the second cake. Dust with icing sugar or a simple icing using just icing sugar and water and finish with a few mint leaves.