Grease square springform pan (24 x 24 cm; alternatively round, 26 cm Ø). Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer).
Chop 300 g chocolate coating and melt with 250 g butter in a hot water bath. Remove from the water bath. Stir in sugar. Mix ground hazelnuts and baking powder. Stir into the couverture mixture. Stir in the eggs one by one.
Smooth the dough in the form. Bake in a hot oven for about 30 minutes. Take out and let cool down.
Coarsely chop the hazelnut kernels and roast them in a pan without fat. Remove from the heat. Mix in honey. Melt 100 g chocolate coating in a hot water bath. Remove the brownie from the tin and cut into cubes (à approx. 4 x 4 cm).
Spread some honey nuts on it. Drizzle chocolate coating in strips over it, let it dry.