Cream the butter and sugar together in a bowl.
Add the egg yolk and mix well.
Sift in the cake flour and almond flour, then mix to combine.
Roll the dough into a log, wrap it in plastic wrap, and chill in the refrigerator until firm.
Slice the chilled dough into even pieces.
Bake in a preheated oven at 180°C (356°F) for 15 minutes.