Sift the flour and salt into a bowl. Rub the butter into the flour until the mixture starts to crumble. Add sugar and cinnamon and mix well. Mix together with the egg yolk and possibly some milk to form a stiff mass.
Place on a countertop sprinkled with flour and knead until smooth. Roll out until the dough is a little less than 2 cm thick and cut out the biscuits.
Place the cut biscuits on a greased baking sheet and bake at around 200 C for 10-15 minutes.