The first thing you need to do is make the sponge. Separate the eggs and mix the egg whites with a pinch of salt in a mixer, until they get hard. Add the sugar and mix until the mixture becomes dense and shiny. Incorporate the egg yolks, baking powder, and flour and mix with a spatula until you get a smooth mix.
Preheat the oven and grease a round cake tin or two sandwich tins. Put the mix in the chosen baking tins and bake for 25-30 minutes at 170 degrees or until the top is firm to the touch and a skewer inserted into the centre of the cake comes out clean.
Once the sponge is baked, take it out of the baking tin and let it cool completely before cutting it in two equal pieces (if you have used one round tin).
Prepare the gelatine as instructed on the pack ready for the next step.
Now we are going to move on to make the cream. You could start this step while the cake is baking. Add the egg yolk, milk and sugar in a bowl and mix all together over a bain-marie, until you obtain a thick cream. Make sure it doesn’t reach boiling point. It has to be hot, but not boil as it will cut the cream.
Once it is ready, take it off the heat and after about five minutes, incorporate the gelatine. Mix well and let it cool down naturally.
Make sure the cream for whipping is very cold, and mix it until you obtain a thick whipped cream.
Once you have the very cold whipped cream and the cream that has reached room temperature, you have to move fast, as this is how the gelatine will be activated.
Start by mixing ⅓ of the cream with the whipped cream, with a spatula, until it incorporates. Do the same for the next ⅓ of the cream, and then for the last batch. You will notice that the cream will start to become very thick.
Use a ring to build the cake. You can also use a large pot and build it upside down. Put the first sponge at the bottom and use some of the liquid in the pineapple on top, to get it a bit most - but not to the point that it gets wet. If you are using ladyfingers, pass them quickly through the pineapple juice, so they don't soak, and then layer them at the bottom.
Add 1/4 of the cream, then top the cake up with the fruits of your choice. Then add the next ¼ of the cream, and put the second sponge over. Add some pineapple syrup, then repeat with the rest of the cream. Smooth the top of the cake, and decorate it with fruits, grated chocolate, etc.
Put the Diplomat Cake in the fridge and let it rest for at least 8 hours - best overnight.