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 '/4-inch slices; place on ungreased cookie sheets. Bake at 400" 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.