In a mixing bowl, combine the room temperature butter, sugar, vanilla sugar (or vanilla extract), orange zest, and salt. Stir until the mixture is thoroughly combined.

Sift the all-purpose flour and potato starch over the butter mixture.

Stir all the ingredients together until a smooth dough forms.

Preheat your oven to 200°C (no fan).

Take the cookie dough and divide it into even-sized pieces. For the best results, use about 25g of dough per piece.

Roll into balls.

Grease the molds you'll be using for the thumbprint cookies. Place one dough ball in each mold.

Press the dough down in the center of each mold to create a nice big circle.

Fill the center of each cookie with cranberry sauce to create the thumbprint.

Bake the cookies in the preheated oven for 12-15 minutes or until golden brown

Once done, remove the tray from the oven and let the cookies cool in the molds.

In a small bowl, whisk together the powdered sugar and orange juice to create the icing.

The icing should be quite thick for piping, so adjust as needed.

Once the cookies have cooled in the molds, carefully knock them out.

Use a piping bag filled with the prepared icing to pipe a squiggle around the top of each cookie.