Mix the soft, room temperature butter with the sugar until creamy, about 10 minutes.
Add the egg and continue mixing until smooth. Turn off the mixer.
Mix the flour with the almond flour, salt, and vanilla sugar.
Spoon the dry ingredients over the buttercream and fold in with a spoon.
The mixture will be slightly soft and sticky but will harden in the refrigerator.
If you find the mixture too soft, add 1-2 tablespoons more flour.
Wrap the dough in cling film and refrigerate for 2-3 hours.
Divide the dough into 2 pieces. Roll one piece out into a 0.3cm (0.12 inch) thin sheet.
The other piece of dough is chilled again.
Cut out stars, fir trees, or any other shape you like, and put them on a baking tray lined with baking paper.
Preheat the oven to 180 degrees Celsius (356 F).
Bake the cookies for 13-15 minutes until lightly browned around the edges.
Remove and place on a cooling rack.
While the first batch are baking, take the other piece of dough out of the fridge and cut into cookies.
Once baked and cooled, cover with jam to taste. I use apricot jam for stars and cranberry jam for fir trees.
Put the cookies in a tin and leave in a cool place overnight. This will help them soften.
The next day dust with sugar and serve with delight.
Enjoy!