Preheat the oven to 350 degrees F (180 degrees C / gas 4). Beat the sugar and butter until pale and fluffy. Sieve the flour and baking powder into the butter mixture. Add the eggs and mix it all together. Then mix the cocoa powder with 8 tablespoons of warm water, until smooth.

Fold the chocolate paste, almonds, and chocolate pieces into the cake mixture. Pour the mixture into a greased baking tin, spreading it out evenly. Bake for about 18 to 20 minutes.

Meanwhile, melt the chocolate sauce ingredients in a bowl over some lightly simmering water. Stir until blended well. When the pudding is cooked, remove from the oven and pour over the chocolate sauce while still hot.