How to make
Heat the oven to 320°F (160°C). In a small heat resistant container, combine the crumbled chocolate with 1/3 cup (75 g) of butter and melt on a low heated stove. Set it aside.
Beat the remaining butter and powdered sugar into the bowl with a mixer for about 5 min. until you get a fluffy cream. Add the eggs one at a time, and then the vanilla.
Sift the flour with the baking powder and baking soda, add this to the main mixture along with the ground hazelnuts and cocoa. Pour the resulting mixture in a 9″ (23 cm) diameter baking form, laid out with baking paper. Bake the cake for 45 min. until a toothpick stuck in it comes out dry.
Let it cool and pour couverture chocolate or chocolate glaze on top. Decorate as desired.