For the sponge in our best ever chocolate cake, you will need:

200g dark chocolate (at least 60% cocoa solids), broken into chunks
200g butter , cut into 1cm cubes
85g self-raising flour
85g plain flour
25g cocoa powder
200g light muscovado sugar
200g golden caster sugar
1 tbsp instant coffee granules
1/4 tsp baking powder
3 eggs
75ml buttermilk

And for the icing:

200g dark chocolate (at least 60% cocoa solids), roughly chopped into small pieces
284ml thick double or pouring cream
2 tbsp golden caster sugar
1 cup grated chocolate (for decorating the top)

(makes one 8-inch cake)

In a large bowl, mix together the two kinds of flour, baking powder, sugars and cocoa powder.

In a small bowl, whisk together the eggs and buttermilk.

Warm the chocolate chunks, butter, coffee granules and 1/2 cup water in a saucepan over low heat until the chocolate and butter are just melted. This mixture must not get too warm or it will create lumps when thrown in with the egg mixture in the next step.

Add the chocolate and egg mixtures to the bowl of flour mixture, stirring into a smooth, silky consistency. Pour into a lined and greased 8-inch cake tin and bake in a preheated oven at 160°C (325°F) – 140°C (275°F) for fan-assisted ovens – for about 1 hr 50 min. Because all appliances differ, check the cake from time to time after 1 and a half hours to see if it is cooked. Test if the cake is cooked by inserting a pin or fork in the middle. If it comes away clean, it is cooked. Turn out onto a rack to cool.

To make the icing, heat the cream and sugar in a pan gently until nearly boiling. Put the chocolate pieces into a bowl. Pour the cream mixture over the chocolate and stir until the chocolate has melted.

When the cake is completely cold, cut it into three slices horizontally. Spread the icing between layers and cover the top and sides completely, using a round-bladed knife. Sprinkle the grated chocolate over the top and serve.