Start with the cream as you want the pudding to cool.
Prepare a pudding from the pudding powder, yolk and milk, pour into a mixing bowl and leave to cool.
To finish the cream, stir the butter and sugar until creamy, stir in the yolk mixture spoon by spoon.
For the dough, beat the egg white until half-firm, pour in the sugar and whip again firmly. Fold in the remaining ingredients.
Spread on a baking sheet lined with baking paper and bake at approx. 180 ° C for approx. 15-20 minutes (depends on the oven, can vary).
After baking, cut into 4 to 5 strips (I always cut the width of the sheet, there will be 5 cuts, this works great with the pizza roller and a ruler), put together with cream when cooled, and the last strip is covered with fondant icing.
Pour chocolate icing into a freezer sack, cut a small hole, spray it lengthways and pull the famous Esterházy pattern with a knife, alternately pulling it from above and below and rather close to each other, looks nicer. Put on the last strip and cut into sections.