Cookies:

3/4 c. firmly packed brown sugar
1 c. butter, softened
1 egg yolk
2 c. all-purpose flour

Frosting:

2 tbsp. butter
1 1/4 c. powdered sugar
1/2 tsp. vanilla
4 to 5 tsp. milk

In large bowl, beat brown sugar and 1 cup butter until light and fluffy. Add egg yolk; blend well. Lightly spoon flour into measuring cup; level off. Stir in flour; mix well. Cover with plastic wrap; refrigerate 15 minutes if necessary for easier handling.

Heat oven to 325°F. Shape dough into 1-inch balls. Place 2-inches apart on ungreased cookie sheets. Flatten to 1 1/2-inch circle with fork dipped in flour.

Bake at 325°F for 10 to 14 minutes or until light golden brown. Immediately remove from cookie sheets; cool completely.

Heat 2 tablespoons butter in medium saucepan over medium heat until light golden brown. Remove from heat. Stir in remaining frosting ingredients, adding enough milk until frosting is of desired spreading consistency; blend until smooth. Spread 1 teaspoon frosting between 2 cooled cookies; repeat.