Preheat the oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer) and line the bottom of a springform pan (26 cm Ø) with baking paper.
For the crumble dough, coarsely grate the chocolate coating. Cream butter, brown sugar and 1⁄2 TL salt with the whisks of the mixer. Mix the grated chocolate coating, cocoa, flour and baking powder. Add to the butter-sugar mixture.
Knead into crumbles with your hands. Press into the mould to form a base, forming a rim approx. 2.5 cm high. Bake in a hot oven for about 15 minutes. Remove from the oven and leave to cool for about 30 minutes.
For the filling, chop the couverture. Heat the butter in a pot and remove from the heat. Melt the couverture in it while stirring. Beat the eggs, sugar and 1 pinch of salt with the whisk of the mixer until foamy.
Stir in warm chocolate butter. Stir in 50 g flour briefly.
Preheat the oven again (electric oven: 200 °C/circulating air: 175 °C/gas: see manufacturer) and cut off the wafers from the chocolate kisses (and use them for other purposes). Place the chocolate kisses evenly distributed on the crumble base.
Carefully pour the chocolate filling over it. Bake in a hot oven for about 15 minutes.
Remove, allow to cool and carefully remove from the mould. Dust with a powdered sugar pattern as desired.