Grease a springform pan (26 cm Ø; approx. 7 cm high) and dust with flour. Coarsely chop the nuts. Put 1/2 apple in a cool place. Peel, quarter, core and dice the rest of the apples. Sprinkle with 3 tablespoons lemon juice
Dice 250 g butter. Peel approx. 2 tablespoons of shavings from 300 g chocolate coating with a peeler. Coarsely chop the rest of the 300 g couverture, melt with the butter in a hot water bath. Cool down a little
Separate eggs. Beat egg whites and 1 pinch of salt until stiff. Beat egg yolk and sugar for about 5 minutes until creamy. Whip the liquid chocolate butter in a thin stream. Sift 175 g flour and baking powder on top and fold in. First fold in the beaten egg white, then the nuts and apple cubes. Spread into the mould. Bake in the preheated oven (electric cooker: 200 °C/circulating air: 175 °C/gas: level 3) for approx. 1 hour (cover after approx. 45 minutes if necessary). Let them cool down
Chop 300 g of chocolate coating, melt in a hot water bath with plate-grease. Wash the rest of the apple, halve, core and cut into slices. Sprinkle with 2 tbsp. lemon juice. Then dab dry, dip half of it into the couverture. Leave to dry a little on baking paper. Using a teaspoon, drizzle some couverture in strips over the chocolate side of the apple slices. Leave to dry
Heat the rest of the chocolate coating again and cover the cake with it. Decorate the chocolate cake with chocolate apples and shavings. Leave to dry