Cream together 1/2 cup butter and 1/4 cup brown sugar.
Add 1 egg yolk; mix well.
Add 1 cup flour.
In small bowl beat 1 egg white until frothy.
In second small bowl put about 1 cup chopped walnuts.
Roll tablespoon-size pieces of dough in egg white, then nuts. Put on ungreased cookie sheets. Let the kids put their thumbs in the middle (even two-year-olds love this!). Bake 5 minutes at 400 degrees F. Continue 15 minutes more at 300 degrees . Put cherry (or other) jelly in depression when cool. To bake these cookies ahead, freeze without the jelly, then add when serving.