How to make
Beat the flour with hot melted butter with a wooden spoon until you get crumbs.
Add the powdered sugar, egg yolks, cinnamon and the citric acid, dissolved in 1 tablespoon of water with 1 nearly full teaspoon of baking soda.
Knead the dough well and shape it into round, semi flat cookies. Arrange them in a lightly greased baking tray and bake them in a moderately heated oven.
