Filled Lemon Cookies

2 cups Butter or margarine, softened
1 cup Powdered sugar -- sifted
4 cups All-purpose flour
1/4 t Salt
2 ts Lemon extract
Additional powdered sugar

Filling:
1 Egg -- beaten
2/3 c Sugar
2 tb Butter or margarine- softened
1 1/2 ts Grated lemon rind
3 tb Lemon juice
1 t Cornstarch

Cream butter; gradually add 1 cup powdered sugar, beating well at medium speed of an electric mixer. Combine flour and salt; add to creamed mixture, beating well. Stir in lemon extract. Flour hands, and shape dough into two 16-inch rolls; wrap in wax paper, and chill several hours. Unwrap rolls, and cut into 1/4-inch slices; place on ungreased cookie sheets. Bake at 400ºF for 8 minutes or until browned. Cool on wire racks. Spoon filling on bottom side of half the cookies, spreading evenly. Place a second cookie on top of filling, top side up, and sprinkle lightly with powdered sugar. Yield: 5 dozen.

FILLING Combine all ingredients in top of a double boiler, stirring until blended. Bring water to a boil. Reduce heat to low; cook, stirring constantly, until thickened and smooth. Chill about 1 hour. Yield: about 3/4 cup.