Chop the butter into pieces, quickly knead with the flour, sugar, vanilla sugar, salt and the two egg yolks (also works in the food processor) until you get a nice ball. Wrap the dough in cling film and put it in the refrigerator, bottom shelf, for a good hour.
Then preheat the oven to 175 ° C circulating air. Dust the worktop with flour, pound the dough flat, roll out cling film over it and roll it out about 5 mm thick (so nothing sticks to the rolling pin).
Cut out any shapes, place them on a baking sheet lined with baking paper a little apart and when the temperature is right, put them in the oven for 7 minutes, second rail from the bottom. Then decorate it as you like or glue it together with jam.