Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Grease a springform pan (26 cm Ø). For the brownie base chop the nuts coarsely. Break 150 g chocolate into pieces. Melt with 125 g butter in a saucepan while stirring at low heat.
Beat the eggs and sugar with the whisk of the mixer for approx. 3 minutes until creamy. Add hot chocolate butter while stirring. Mix flour, cocoa and baking powder. Quickly stir into the chocolate mixture.
Pour into the mould and smooth it down. Ca. 1⁄3 Spread nuts on top. Bake in a hot oven for about 18 minutes. Take out and let cool down.
For the nut topping, lightly caramelise the remaining nuts and honey in a pan while stirring. Spread on a sheet of baking paper and let it cool down. For the ganache, break 150 g chocolate into pieces.
Bring 150 g cream to the boil and remove from the heat. Melt chocolate in it while stirring. Let it cool down.
For the filling, whip the sour cream and 150 g cream until stiff with the whisks of the mixer. Stir the fruit spread until smooth and fold loosely into the sour cream with a tablespoon. Carefully remove the brownie base from the mould.
Spread the sour cream on top. Chill for about 30 minutes.
Carefully spread the ganache on the sour cream. Sprinkle caramelised nuts over it. Keep cool until serving.