Preheat the oven to 180 degrees (350F)

Melt the butter and chocolate over a bain marie

Separate the eggs, adding a pinch of salt to the egg whites and whisking until stiff peaks form

Add the sugar to the egg yolks and also whisk until light and creamy

Once the chocolate has cooled, add to the egg yolks and sugar

Sieve the flour and baking powder together and fold into the wet ingredients

Finally, incorporate the egg whites in sections into the mixture, folding very gently and taking your time until there are no white lumps

Line a cake tin with parchment paper and pour in the cake mixture

Bake for around 20 mins until a knife comes out mostly clean

Let it cool on a wire rack before serving