12 Tablespoons salted butter, room temperature (( 1 1/2 sticks))
1¼ cup powdered sugar
1½ teaspoons vanilla extract
2½ cups marshmallow fluff
Instructions:
Heat oven to 350°F. Line two large cookie sheets with either parchment paper, Silpat, or lightly spray with nonstick cooking spray.
In large bowl, beat together 1 box devil's food cake mix, 3.9 ounce box instant chocolate pudding mix, 3 large eggs, 3/4 cup water and 1/2 cup vegetable oil until thoroughly combined (batter will be thick).
Pour batter into a 1 gallon ziploc bag and seal. Cut a hole off of one of the bottom corners.
Pipe batter into 36 small circles onto cookie sheets about 1-inch apart (this will allow for spreading).
Bake 10 to 12 minutes until set. Cool 2 minutes; remove from cookie sheets and place on cooling rack. Cool completely before filling.
With electric mixer on medium speed, in a medium-sized bowl, beat 12 Tablespoons salted butter, room temperature and 1¼ cup powdered sugar until fluffy then beat in 1½ teaspoons vanilla extract.
Beat in 2½ cups marshmallow fluff until incorporated. Cover bowl with plastic wrap and refrigerate filling until slightly firm, about 30 minutes.
Once cookies are cooled, spread filling (about 2 Tablespoons - you want a thick filling so use your best judgement) on flat side of one cookie. Top with the second cookie, flat side down to make a sandwich.
Then enjoy! If not eating immediately, I suggest wrapping each one individually in plastic wrap and storing in the refrigerator for up to 3 days.