Preheat the oven to 175 ° C fan oven. Line a baking sheet with parchment paper.
Mix the butter, sugar, vanilla sugar and salt until foamy, then add the egg yolks.
Mix the flour and baking powder well and sift over the butter-sugar mixture. Add the cranberries and stir in with a wooden spoon until all the ingredients are well mixed.
Shape the dough into a thick roll. Then place the poppy seeds on a flat plate and roll the rolling pin in it until it is completely covered. Wrap in cling film and let rest in the refrigerator for 60 minutes.
Remove the dough from the foil and cut into 1 cm thick slices with a sharp knife. Place the cookies on the baking sheet with sufficient space between them and bake for 8-10 minutes.