Pre preparation; Using blender or other way prepare walnuts powder. Leave butter at room temperature to soften.
2
Mix butter with egg yolk using electric mixer, then add other dry ingredients and then lemon juice little by little until you get a compact dough (you will need 2 oven trays for this quantity).
3
Preheat the oven to 180C and bake for 15-20min, they should stay white).
4
Let it cool down and then spread apricot jam onto one piece and top it with another (like a sandwich). Coat it with powder sugar and place in a fridge for several hours, even better for one night. It can stay in the fridge for up to a week.