Weigh the oat flakes medium fine with a weighing knife and toast them with 3/5 of the sugar in a frying pan until golden brown. Cool.
Cream butter, egg and the remaining sugar. Gradually add the oatmeal and all the other ingredients and make a dough.
Roll out the dough to a thickness of 2 to 3 mm and cut out rings. Put the rings on a buttered baking tray, mix the egg yolks with a little bit of milk and brush the rings with it. Bake at 180 °C for 15 minutes.