Thimble Cookies

These are one of my all time favourite cookies, bar none. They are best just slightly frozen, in my opinion.

½ cup butter
¼ white sugar
1 egg, separated
1 tsp vanilla
1 cup sifted flour
Finely chopped nuts
Jelly

Directions:

Cream butter and add sugar gradually and mix well
Add well-beaten egg yolk, vanilla and flour. Mix well
Shape into balls and the size of a walnut.
Dip in unbeaten egg white, then into finely chopped nuts.
Dent in the center of ball with thimble (you can use the tip of your thumb)
Place on cookie sheet and bake for 5 minutes at 350 degrees and dent again.
Bake for another 15-20 minutes more
When fully cooked, fill with jelly of your favourite jelly while still warm.