Cream the sugar into the butter or spread until it is light and fluffy.
Add the eggs one by one, mixing well after each.
Sift in the flour and fold in.
Zest the lemons and fold in.
If you have three 20 cm tins, prepare them and put one third of the mixture into each. I only have two so I made two layers first, then the third one afterwards.
Bake at 180 degrees for approx 20 minutes, or until the cake is golden brown and cooked through.
Leave the cakes to cool for a few minutes, remove from the tins and then leave the, to cool completely.
Make the lemon drizzle by mixing together the lemon juice and caster sugar. Make holes in the cakes using a skewer or cake tester, and spoon the drizzle over each layer. I did this when my cakes were almost cool, as I didn't want them to go to soft when warm in case they broke.
Make the ganache: break the chocolate up and place the chocolate and cream in a large microwaveable bowl. Microwave on high for 30 seconds, stir well, then heat for ten seconds at a time, stirring afterwards, until smooth. Place the ganache in the fridge to cool. After about thirty minutes, whip using a handheld mixer for a few minutes, until thick.
Make your Chantilly cream: put the double cream, icing sugar and lemon zest in a large bowl. Whip using a handheld mixer until it has firm peaks.
To assemble, level the bottom layer, spoon on some white chocolate ganache. Pipe the cream around the edges. Add the next levelled layer and repeat. Add the final layer, pipe cream in the centre, spoon the ganache on, and decorate with lime zest curls and lemon zest.