Preheat oven to 325 degrees F.
Combine dry cake mix with oil, water and eggs. Stir until combined. Use an ice cream scoop or two spoons to drop the scoops of dough onto an ungreased cookie sheet 2 inches apart. Bake for about 13 minutes. Cookies should be firm enough to handle, but not overly done and crispy. Cool completely on a wire rack.
Meanwhile, beat together the butter and powdered sugar. Add the marshmallow cream and vanilla, blending until smooth. Spoon 1-2 tablespoons of the filling onto the bottom of a cooled cookie. Press the bottom of another cookie on top of the filling to make a sandwich. Repeat with remaining filling and cookies.
Store pies between layers of waxed paper in an airtight container and refrigerate for up to 2 days.
by The Savvy Kitchen