1 cup butter or margarine, softened
2/3 cup sugar
2 egg yolks
1/2 tsp. vanilla extract
2 1/4 cups all-purpose flour
1/2 tsp. salt
Chocolate Frosting (recipe follows)

Cream butter;  gradually add sugar, beating until light and fluffy.  Add egg yolks, one at a time, beating well after each addition.  Stir in vanilla.

Combine flour and salt;  add to creamed mixture, mixing well.  Chill

Roll dough into 1 inch balls;  place about 2 inches apart on ungreased cookie sheets.  Press thumb in each cookie, leaving an indentation.  Bake at 300 degrees for 20 - 25 minutes (I think it takes a lot less).  Cool on wire racks.  Place 1/2 teaspoon chocolate frosting on each cookie.

Yield:  3 1/2 dozen

This is Judy's favorite cookie.
 
 

Chocolate Frosting
1 cup sugar
1/4 cup cocoa
1/4 cup milk
1/4 cup butter or margarine
1/2 tsp. vanilla extract

Combine sugar, cocoa, and milk in a heavy saucepan.  Bring to a boil and boil 1 1/2 to 2 minutes, stirring constantly.  Remove from heat.  Stir in butter and vanilla.  Beat until mixture is of spreading consistency.  You'll think your arm is about to fall off, but it's worth it.