Cream butter or margarine, and sugar in a mixing bowl until fluffy (3-5 minutes)
Add in eggs and vanilla and beat well.
In a separate bowl, sift together flour, cocoa powder, baking powder, baking soda, and salt.
Add the flour mixture to the creamed butter mixture, and add in the milk, mixing well.
Press into slabs, and refrigerate for 1-2 hours or overnight.
Shape dough into two 10 x 1 1/2 inch rolls and wrap each roll into wax paper; chill for several hours or overnight. Alternatively, refridgerate the dough to be rolled out flat and cut out with cookie-cutters
When you take the dough out of the refrigerator, let it sit on the counter for about 10 minutes that way it is easier to work with.
Roll the dough to 1/8 inch thick and use biscuit cutters to cut circles
Bake slices on un-greased cooking sheet at 325 degrees for 9 min.
Let the cookies sit on the cookie sheet for 5 minutes, then remove and place them on a wire rack so they can cool
.Once the cookies are fully cooled, assemble the cookies sandwich-style with the mint filling
