
Preheat the oven to 170C and butter and line a 23cm cake tin. Sift together the flour, salt and baking powder. In a bowl, over a pan of hot water, melt the chocolate and butter together. Whisk the eggs and slowly add the sugar. Beat in the chocolate mixture and gently fold in the flour and chocolate buttons. Pour into the cake tin and bake for 35 minutes until the surface is set but a skewer comes out with a little of the mixture clinging to it. Remove and cool slightly before placing on a wire rack to cool. Cut into pieces and keep in a tin or in the fridge. I find these easier to separate if you slice them up then put them in the fridge for a couple of hours before separating them, as they can be quite delicate.