Directions
Preheat your oven to 350 degrees F. In the bowl of your mixer, cream the butter and sugar until light and fluffy. Beat the egg yolks in one at a time. Add the vanilla. Stir in the flour and ground nuts until well combined.
Scoop 1/2 ounces of dough and roll into balls about one inch in size. Place on an ungreased cookie sheet. Bake for five minutes on the center rack of your oven. Remove the cookies from the oven, make an indentation in each and fill with jam. Return the cookies to the oven to bake for 10 more minutes. Cool the cookies for a few minutes in the pan before removing to cool completely.
Store in layers separated by waxed paper in a well-sealed container. Freeze for longer storage.