Ok, Martha Day's Complete Baking calls the original recipe of this adapted version Rich Chocolate Nut Cake, but it really IS a chocaholic's dream. It is like eating truffles, so serve it in small helpings.
Preheat a 350°F/180°C/Gas 4 oven. Line a 9x2in (23x5cm) round tin with greaseproof paper and grease.
Melt butter and chocolate together in the top of a double boiler, or in a heatproof bowl set over hot water. Set aside to cool.
Sift cocoa into bowl. Add sugar and eggs and stir until just combined. Pour in the melted chocolate mixture and brandy.
Toast the hazelnuts without oil in a skillet over medium low heat. Coarsley chop the toasted nuts. Fold three-quarters into the mixture and then pour the mixture into the prepared tin.
Set the tin inside a large tin and pour 1in (2.5cm) of hot water into the outer tin. Bake until the cake is firm to the touch, about 45 minutes. Let stand 15 minutes, then unmould and transfer to a cooling rack.
Wrap the cake into greaseproof paper and refrigerate for 6 hours.
For the glaze, combine the butter, chocolate, milk and vanilla in the top of a double boiler or in a heatproof bowl set over hot water, until melted.
Place a piece of greaseproof paper under the cake, then drizzle spoonfuls of glaze along the edge to drip down and coat the sides. Pour the remaining glaze on top of the cake.
Cover the sides of the cake with the remaining nuts, gently pressing them on with the palm of your hand.