Pre heat the oven to 180'c
Brush 2 6inch non stick baking tins with the sunflower oil and fit the base with a circle of parchment paper to prevent any sticking.
Fill a large saucepan with water and bring to a gentle simmer.
Break the eggs and place in a large mixing bowl, alongside the caster sugar and the lemon zest.
Place the bowl on top of the pan of water and vigorously whisk for 5 minutes until the mixture resembles a thick custard.
At this stage, gradually sieve the flour into the mixture. When all the flour is sieved, very gently fold the flour through the egg mix using a spatula.
Divide the mixture into the 2 baking tins. Place in the oven for 28 minutes until cooked. Remove the cakes from the tins and allow them to cool on a wire rack.
Wash one tin and dry well, ensuring there is no water. Line the tin with ace-tape. Place one sponge back into the tin, ensuring the flatter side on facing the surface.
Beat together the egg yolks and the sugar until pale and fluffy. Add the vanilla extract. Mix well and then sift in the flour, folding it in as you go.
Bring the milk to the boil and then add to the mixture, stirring all the time. Return the mixture to the pan and continue stirring over a medium heat until the mixture is thick and coats the back of a spoon. Remove from the heat and whisk in half of the butter. Allow to cool and then whisk in the remaining butter. The mixture should be thick, creamy and smooth.
Remove the green part of the strawberries and slice them lengthways. Ensure they are all the same height. Making sure the flat side of the strawberries is at the bottom. Line the outside of the tin with the strawberry slices. If you are finding that the strawberries are not staying in position, try rubbing some sunflower oil round the tin.
Chop any excess strawberries and trimmings, sprinkle with icing sugar, and set aside for a few minutes. Use the resulting juice to drizzle over the sponge, and spoon the chopped strawberries onto the bottom.
When all the strawberries are in place, slowly pour the custard into the centre of the tip, ensuring it covers in the tips of the strawberries. Gently shake the tin to ensure the custard is completely fat. Then place the second sponge on top, ensuring that the flat side of the sponge remains upwards. Gently push the sponge down so the sponge is touching the custard.
Allow the cake to cool and set in the fridge for an hour.
When its set, generously sprinkle the cake with icing sugar and serve.
«Try topping the cake with marzipan to increase the decadence!!»