1 cup butter
1 1/2 teaspoons vanilla extract
2 eggs
1 1/2 teaspoons cornstarch
1 (1 ounce) package white icing
1/4 cup fresh lemon juice
1 teaspoon lemon zest
In a large bowl, cream together the butter, vanilla extract, eggs, cornstarch and white icing until smooth. Mix lemon juice and lemon zest into creamed mixture. Pour into cookie shells and chill overnight.
While cookies are chilling, prepare lemon custard over a double boiler in the microwave for 3 to 4 minutes.
Remove cookies from refrigerator and creamed them together with lemon custard. Chill overnight in refrigerator before cutting into squares.