For the buttercream, stir the pudding powder, 75 g sugar and 100 ml milk until smooth. Bring 400 ml milk to the boil, remove from the heat. Stir in the pudding powder, bring to the boil again while stirring and simmer for about 1 minute. Put the pudding in a bowl, cover directly with foil and let it cool down at room temperature.
Store 250 g butter at room temperature. For the dough, whisk 150 g butter, salt, 200 g sugar and vanillin sugar with the whisk of the hand mixer until foamy. Stir in the eggs one after the other. Mix flour, starch and baking powder, stir alternately with 5 tbsp. milk into the fat-egg-cream.
Grease a Frankfurt wreath form or ring form (1.4 litres capacity; 22 cm Ø) well and dust with flour. Pour in the dough and smooth it down. Bake in the preheated oven (electric cooker: 175 °C/circulating air: 150 °C/gas: level 2) for 30-40 minutes. Let cool slightly on a cake rack. Turn out of the tin and let cool completely.
Whisk the butter, which has been stored at room temperature, until creamy white (approx. 15 minutes) with the whisk of the hand mixer. Stir in the pudding by the spoonful. Stir jelly until smooth. Cut the cooled cake twice horizontally. Spread the redcurrant jelly on the bottom layer. Spread 1/4 of the cream on the jelly and smooth it down. Place the second cake layer on top and spread with another quarter. Place the third base as a lid on top.
Pour some cream into a piping bag with a star-shaped spout. Spread the rest of the cream all around. Sprinkle the wreath with brittle. Spray the rest of the cream as tuffs on the wreath. Halve the cherries and place them on the tuffs. Chill for about 2 hours.