Drain the cherries on a sieve. Place the fat, sugar, vanilla sugar and salt in a mixing bowl and whisk until foamy. Stir in the eggs one after the other.
Mix flour and baking powder and stir in portions alternately with four tablespoons of milk. Grease a springform pan (26 cm Ø) and pour in 2/3 of the dough. Smooth out. Add cocoa and the rest of the milk to the remaining dough and mix.
Spread evenly on the light-coloured dough. Spread the cherries, up to 16 for decorating, on top. Bake in the preheated oven (electric oven: 200 °C/ gas: level 3) for about 40 minutes. Let cool on a cake rack.
In the meantime, mix the pudding powder with four to five tablespoons of milk for the buttercream. Put the remaining milk and sugar in a pot and bring to the boil. Remove from heat and stir in the pudding powder.
Bring to the boil again. Leave to cool while stirring occasionally. Beat the soft butter with the whisk of the hand mixer until white and stir in the pudding by the spoonful. Spread 2/3 of the buttercream on the cake base and smooth it down all around.
Melt the chocolate coating in a warm water bath. Pour into a small freezer bag. Cut off a small corner and decorate the cake with wavy lines. Let it dry. Pour the rest of the buttercream into a piping bag with a star nozzle and squirt 16 tuffs all around the cake.
Place the remaining cherries on top. Chill the cake until the buttercream has set.