For the buttercream, stir the pudding powder, 120 g sugar and 100 ml milk until smooth. Bring 650 ml milk to the boil, remove from the heat. Stir in the pudding powder, bring to the boil while stirring and simmer for about 1 minute.
Place pudding in a bowl, cover directly on the surface with foil and allow to cool at room temperature.
For the dough, mix 250 g butter, 250 g sugar, salt and vanilla sugar for about 8 minutes with the whisk of the hand mixer until creamy. Stir in the eggs one by one. Mix flour, starch and baking powder and stir into the fat egg mass alternately with the cream.
Grease a ring mould (2.8 litres capacity) and dust with flour. Pour in the dough. Bake in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for approx. 40 minutes. Take out the cake and let it rest in the tin for about 10 minutes.
Drop onto a cake rack and let it cool down.
Whip 375 g room-warm butter with the whisk of the hand mixer for approx. 15 minutes until creamy white. Stir the pudding until smooth, stir in the butter by the spoonful. Stir jam until smooth. Cut the cooled base 2 x horizontally.
Spread the jam evenly on the lower and middle base. Spread about 1/4 of the cream on each. Layer the cake layers again. Spread the rest of the cream all around and chill for at least 2 hours.
Sprinkle the outside and inside of the wreath with brittle. Sort the raspberries. Decorate the cake and cut into pieces.