Rich, dark, dense...this is the ultimate Easter cake for committed chocolate consumers. It's one of my favourites as it isn't too sweet, so the flavours of the chocolate are able to assert themselves. The technique for making it is quite unusual: you fold in beaten egg whites as you would for a soufflé in order to make it rise up as high as possible in the oven, then you sit plates on top of it while it cools in order to compress the air so the middle becomes delicious and fudgy. Much like a grown-up brownie. It's pretty fool-proof and if you happen to undercook it, the middle just becomes a bit moussey (see pic, below), which is arguably no bad thing. This cake is also perfect for anyone avoiding gluten.
225g unsalted butter, cut into cubes
300g high-quality 70% cocoa dark chocolate, broken into pieces
8 eggs, separated
150g golden caster sugar
1/2 teaspoon sea salt
3 tablespoons cocoa powder, plus extra to decorate
Icing sugar, to decorate
Heat the oven to 180C/350F/gas 4 and grease and line a 23cm cake tin.
Place the butter and chocolate in a large bowl over a pan of simmering water (making sure the water doesn't touch the bottom of the bowl) and gently heat until melted, stirring only occasionally. Take off the heat and leave to cool slightly.
Meanwhile, whisk the egg yolks with sugar until thickened and pale, then stir into the cooled melted chocolate along with the salt and cocoa.
In a separate, clean bowl, whisk the egg whites until you have stiff peaks. Stir two tablespoons of the whites into the rest of the mix to lighten, then fold half the remaining whites into the chocolate and once incorporated, fold in the remaining half, trying not to overmix in order to keep it fluffy. Pour into the prepare cake tin, then place in the middle of the oven for 35-45 minutes until risen and cracked on top, but with a very slight wobble in the middle. Take out the oven and place a piece of greaseproof paper on top, followed by a stack of small plates (or 1 plate and something to weigh it down) that just fit within the edges of the tin. Leave to cool completely.
Once cool, take out the tin and dust the top with a little icing sugar followed by a little cocoa. Slice up and serve with crème fraîche. Will stay delicious for up to 5 days.