In a container on the heat, melt butter, add the powdered sugar, milk and grated lemon rind. Remove the warm mixture from the heat and stir in the 1 1/5 cups (300 g) of flour.
Knead well and roll the dough out into a sheet. With a wineglass, or shapes, cut out biscuits. Brush them with egg yolk and bake in a moderate oven, in a tray with baking paper.
Dip the ready biscuits in chocolate spread on one side or halfway in it.