Delightfully borrowed from AllRecipes, slightly altered.
Makes 2 dozen
1 cup butter
1/2 cup confectioners' sugar
2 cups all-purpose flour
1 teaspoon lemon zest
1/2 teaspoon salt
1/2 tsp Lemon Juice (if needed for dryer dough)
INGREDIENTS (Cookie Filling)
1 egg, beaten
2/3 cup white sugar
1 1/2 teaspoons lemon zest
3 tablespoons lemon juice
1 1/2 tablespoons butter
3 tbs cornstarch
1-2 cups powdered sugar
In a medium bowl, cream together butter and confectioners' sugar until light. Stir in the lemon peel, flour and salt. Cover bowl, and chill for about 1 hour. If your dough was dry, you could add in lemon juice.
Preheat oven to 400 degrees F (200 degrees C).
Flatten teaspoons of dough onto cookie sheets, and bake for 5 to 8 minutes, until light brown just a weeeeee bit on the edges. Remove from baking sheets to cool on racks.
To make the filling, combine the beaten egg, sugar, lemon zest, lemon juice, cornstarch and butter in the top of a double boiler over high heat. Stir until thick (10-15 min).
Remove from heat and add enough powdered sugar to form a thick movable paste. Sandwich cookies with filling. Remember that if your filling is still super hot the cookies might slide a bit, I recommend letting the batter cool for just a bit to prevent this.