1. Preheat the oven to 180 Degrees and butter a baking tin that is small and round.
2. Place the chocolate and butter in a bowl and prepare a pot of water to simmer gently. When the water is simmering place the bowl carefully above the water and let the butter and chocolate melt, stirring often so that the mixture doesn't burn and stick to the bottom.
3. In another bowl, place 3 egg whites with half a teaspoon of caster sugar and whisk for about 3-4 minutes until stiff white peaks form.
4. In a bigger bowl, place the egg yolks, the sugar and the slowly add the flour and continue whisking for 3-4 minutes.
5. Make sure that the butter and chocolate mixture is still hot and add into the flour, egg yolks and sugar mixture. If it is too thick, add a small amount of hot water.
6. When this mixture has no lumps, add in the egg white mixture, a third at a time.
7. When the mixture is complete, pour into the baking tin and cook in the oven for 20 minutes.
8. Decorate the cake how you like with frosting and fruit. I chose a yoghurt based frosting with raspberries.