In a small bowl mix together the yolks, butter and salt. Chill for 20-30 minutes.
Mix the zest, limoncello and vanilla, let sit 20-30 minutes.
In a the stand mixer whisk the flour and sugar add the chilled yolk mixture and zest mixture, combine on low (it will be crumbly), then increase to #2 speed and add the half and half one tablespoon at a time until almost combined.
Move the dough to a lightly floured flat surface and gently knead to form a compact soft dough. Wrap in plastic wrap and chill 60 minutes. Roll on a lightly floured flat surface to ¼ inch thick and cut out with medium cookie cutters, place them on parchment paper lined baking sheets.
While the oven is pre-heating to 350F/180C chill the cookies for 15-20 minutes. Bake for 12-15 minutes or until edges start to turn golden brown. remove from the oven and let cool 10 minutes on the pan then move to a wire rack to cool completely. Serve plain, dusted with powdered sugar or drizzled with a limoncello glaze. Enjoy!
FOR THE GLAZE
Stir together the sifted powdered sugar, limoncell or limoncello cream or milk until smooth. Add more or less cream to reach desired thickness.
Notes
If you find the dough too dry then add a bit more cream.Once the glaze has set, store limoncello cookies in an airtight container for up to one week. Use wax paper between layers to avoid sticking. Skip cutting out cookies andflash freeze balls of dough on a parchment paper lined baking sheet then transfer frozen dough to a freezer safe bag. Freeze for up to 3 months. Thaw completely before baking.Freeze unglazed baked cookies in an airtight container for up to two months. Thaw then top with glaze as desired and enjoy.