1. Pre-heat the oven to 180°C/gas 4.
2. Grease and line an 6″ cake tin.
3. Sift the flour and baking powder, returning the sifted-out bran to the bowl.
4. Cream the butter with the sugar until light and fluffy.
5. Add the eggs, a little at a time, beating between each addition.
6. Using a metal spoon, fold in the milk, and sifted flour and baking powder, mixing thoroughly.
7. Add about two-thirds of the chopped chocolate, together with the ground hazelnuts.
8. Spoon the mixture into the prepared tin, levelling the surface. Sprinkle with the chopped hazelnuts and the remaining chocolate.
9. Bake in the centre of the oven for 1 hour, then cover the cake with a sheet of greaseproof paper to prevent the nuts from burning. Bake for 30 minutes more or until the centre feels springy when lightly touched.
10. Release from the tin and leave to cool.