Chocolate sandwich cookies with three fillings

1. Preheat oven to 350°F.
2. Cookies: in bowl, beat butter, sugars and vanilla until well blended.
3. Add egg whites; beat well.
4. Stiri together flour, cocoa, salt and baking soda; add to sugar mixture, beating until well-blended.
5. Refrigerate dough about 1 hr. Or until firm enough to handle.
6. Greasei or spray cookie sheet.
7. Shape dough into 1" balls.
8. Place on cookie sheet.
9. Using fingers, flatten each ball into a 2" circle.
10. Bakei for 7 mins.
11. Or until set. Cool 1 min. , remove to wire rack.
12. Cool completely.
13. Using half of the cookies, spread about 1 ½ t. of desired flavored filling on each cookie.
14. Top with remaining cookies.
15. Fillings: in small bowl, beat butter and ¼ c. sugar until well bleneded.
16. Gradually and other ingredients until well blended and of desired consistency.
17. Adjust amount of milk if needed.
18. Each makes about 2/3 cup.