Step-by-step preparation:

Kneading the dough: In a large bowl, cream the softened butter with sugar (about 200 g) and egg. Add mayonnaise and vanilla sugar, mix thoroughly until smooth.

Working with flour: Gradually add the sifted flour (along with baking powder). Knead an elastic, soft dough that does not stick to your hands.

Shaping: Pinch off small pieces of dough and roll them into walnut-sized balls.

Sugar crust: Dip each ball with one side in a saucer of sugar.

Baking: Place the balls on a baking sheet lined with parchment, sugar side up, pressing them slightly to form a flat base. Bake in an oven preheated to 180°C for 20–25 minutes until lightly golden.

Assembly: Let the cookies cool completely. Take two halves, spread the flat sides with thick jam or marmalade, and stick them together tightly.

Enjoy!