Chocolate Brownie Gateau

450g / 1 lb plain chocolate
225g / 8 oz unsalted butter, plus more for greasing
3 eggs
225g / 8 oz light muscovado sugar
75g / 3 oz self-raising flour
1 tsp vanilla extract
175g / 6 oz pecan nuts, roughly chopped

For the filling:
150ml / 3/4 pint double cream
100g / 3 1/2 oz plain chocolate, broken into pieces

For the chocolate curls:
100g / 3 1/2 oz plain chocolate
100g / 3 1/2 oz white chocolate

Preheat the oven to 190ºC / fan oven 170ºC / gas mark 5. Grease 2 round 17.5cm / 7in sandwich pans and line their bottoms with baking paper. Roughly chop 115g / 4 oz of the chocolate and set aside.

Break the remaining chocolate into pieces and melt, with the butter, in a bowl set over a pan of hot water. Beat together the eggs and sugar. Stir in the melted chocolate, sift in the flour and add the vanilla extract, the chopped nuts and chopped chocolate.

Divide between the sandwich pans and bake for about 30 minutes, until the surface has a sugary crust and feels firm. Loosen the edges with a knife and turn up-side-down on a wire rack covered with greaseproof paper. Leave the cakes in the pans until cool, then remove the pans.

Make the filling: put the cream in a pan with the plain chocolate and heat gently until the chocolate melts. Allow to cool, then whisk until stiff and use to sandwich the cakes together.

Make the chocolate curls: melt the plain and white chocolate in separate bowls. Using a teaspoon, place thin lines of white chocolate on a marble slab or clean smooth baking sheet, leaving a gap of the same width between the lines. Fill the gaps with plain chocolate and leave to set. When it is just set but not brittle, push a sharp knife across the surface at an angle of about 45 degrees; alternatively, draw a potato peeler over the surface of the smooth side of a large chocolate bar to form curls, or use a clean paper-stripping knife held at a slightly lower angle. Decorate the top of the cake with the curls and serve this delicious Chocolate Brownie Gateau.