Spook-tacular Chocolate Sandwich Cookies

I need to take cookies to Drew's class party tomorrow, so I decided on these yummy chocolate sandwich cookies. Easy and delicious...

Easy Chocolate Snickerdoodles
2 boxes chocolate cake mix
1 tsp vanilla extract
4 eggs
2/3 cup oil
Coating: 1 cup sugar and 1 Tbsp. cinnamon

Mix together until well blended. Roll into 1 inch balls and coat with sugar and cinnamon mixture.  Bake at 350 degrees for 8-10 minutes. For sandwich cookies, cool then frost bottom side with Whoopie Filling and top with a second cookie. Makes around 30 sandwich cookies.

Whoopie Pie Filling
2 egg whites
1 tsp vanilla
2 Tbsp. flour
1 Tbsp. milk
1 cup shortening (I use butter flavored)
4 cups powdered sugar
Blend together egg whites, vanilla, flour and shortening.  Add powdered sugar and milk. If too sticky, add another Tbsp milk. If too runny, add 1/2 cup powdered sugar. For holiday cookies, add food coloring.