Spray muffin mini-muffin tin with non-stick spray. In large bowl combine cake mix, flour, water, oil and eggs.
With an electric mixer, beat at medium speed until smooth, 2-3 minutes. Scoop batter by rounded teaspoons into muffin tins-- only ⅓ way filled. Bake until puffed, approximately 8-10 minutes. Let cool 2 minutes.
Remove to wire racks to cool completely.
With a small spoon, spread 1½ teaspoons marshmallow creme onto the flat side of each cookie.
Divide blueberries onto ½ the cookies.
Top with remaining cookies to make sandwiches. Serve immediately or store in airtight container in refrigerator (layer sheets of waxed paper between each layer).
Recipe by My Judy the Foodie at https://www.myjudythefoodie.com/2016/07/4th-july-whoopie-pies/