In large bowl, cream 1 cup butter with 3/4 cup brown sugar until light and fluffy. Add egg yolk and mix well. Then add flour until dough forms. Chill for at least fifteen minutes.

Preheat oven to 325 degrees F. Roll dough into 3/4" balls and place on cookie sheet.

Flatten to 1/8" thickness by pressing two times, in crosswise pattern, with tines of a fork. Bake at 325 degrees F for 8-10 minutes until cookies just begin to turn very light brown around edges. Remove from cookie sheets and cool on wire rack.

In saucepan, melt 1/4 cup butter (NOT margarine). Cook over low heat until butter just begins to brown, watching carefully. Remove from heat and blend in powdered sugar, vanilla, and cream until desired spreading consistency.

Sandwich two cookies together with frosting. Makes about 4 dozen cookies.