Preheat oven to 300°F.

Cream butter, blend in sugar, add egg yolk, beat until light. Blend in flour.

Roll dough into small balls about 1-inch in diameter. Slightly beat egg white with fork. Dip cookie in egg white. Roll in nuts and place on greased cookie sheet. Make a depression in the centers.

Bake for 5 minutes at 300°F.

Remove from oven. Press down centers again. Continue baking 30-35 minutes. Fill centers with bits of candied cherries of tart jelly.

Yield: 2 dozen.