In a large bowl, combine the flour, softened butter, powdered sugar, egg, egg yolk, salt, lemon zest, and vanilla sugar. Knead the mixture until it forms a smooth shortcrust pastry.

Wrap the pastry in plastic wrap and refrigerate it for about 30 minutes.

Once chilled, flour your surface and roll out the pastry to about 3 mm thick.

Use a cookie cutter to cut out cookies and place them on a baking sheet lined with baking paper.

With a smaller cookie cutter, cut out an equal number of cookies with a hole in the middle. Place these on a separate baking sheet.

Preheat your oven to 160°C (325°F) with the convection setting.

Bake the cookies until they are light golden brown. Allow them to cool completely.

Dust the cookies with holes with a little powdered sugar.

On the cookies without holes, spread a smooth layer of redcurrant jelly or apricot jam.

Carefully place the powdered sugar-dusted cookies on top of the jam-covered ones.

Allow them to dry for a bit to ensure they stick together.