You will need for the cake
300g butter, softened
o 300g golden caster sugar, plus a little more to make a syrup
o Zest of 2 unwaxed lemons
o 5 large free-range eggs
o 350g self-raising flour
o 2 tsp baking powder
o 2 tbsp chopped thyme leaves
o 3 large courgettes (500g), coarsely grated
For the icing
o 200g salted butter, softened
o 200g mascarpone
o Zest of 2 unwaxed lemons, plus the juice
of 1 lemon for the syrup
o 900g icing sugar, sifted
How to make:-
1. Measure out the butter for the cake and the icing and place in separate bowls at the back of the Aga to soften.
2. If not using an Aga, heat your oven to 180°C/gas mark 4. Lightly grease a 24cm round springform cake tin. (If you have two tins you can bake two separate sponges
and reduce the cooking time.)
3. Put the cake ingredients (minus the courgette) into a large bowl and beat together until perfectly combined and creamy in appearance – a stand mixer
is perfect for this.
4. Fold in the courgette and pour the mix into the cake tin. Lightly smooth over the top. Place the grid shelf on the floor of the baking oven and the tin on top. This is a long bake for a sponge cake at one hour 10 minutes (at least, it was in my Aga. You’ll need to keep an eye on your cake and adjust according to the foibles of your Aga). If the top is browning too quickly, slide in your cold plain shelf after 20 minutes on the second set of runners.
5. For two-oven Agas, place the grid shelf on the floor of the roasting oven and your deepest roasting tin on top of it. Place your cake tin in the roasting tin and the cold plain shelf on the second set of runners. This will need changing over after 25 minutes with another cold plain shelf or a baking tray while the original one cools down. (Note that it’s a really good idea to have two plain shelves, regardless of how many ovens you have. Also it’s good to have the deepest Aga roasting tin, as these fit onto the runners and negate the need for the grid shelf.)
6. Check the cake is cooked through by inserting a skewer. If it comes out clean, the cake is done. Remove from the oven and allow to cool in the tin for 20 minutes.
Mix a little caster sugar with the juice of a lemon, then skewer the top of the cake in several places and pour over the syrup just as you would for a lemon drizzle cake.
7. Carefully remove the cake from the tin and place on a rack until it has cooled completely.
8. Make the icing by whisking all the ingredients together until smooth and fluffy.
Once the cake is cooled, carefully cut in half to create two sponges.
9. Use some of the icing to sandwich the sponges together, then use a palette knife to smooth the rest of the icing overthe cake. Chill for 20 minutes before