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.
The Yankee Cook's assistant, who has made these for three generations of her family, suggests adding 1 teaspoon of vanilla to the dough. She finds the cookies tend to puff up in the oven, so she takes them out after 5 minutes and uses the handle of a wooden spoon to re-press the thumbprints, then finishes baking, secure in the knowledge there'll be enough room for the jelly.