Preheat the oven to 375 degrees.

In mixer bowl, mix together Brownie Bliss Mix-up, butter and egg. Mixture will be crumbly but hold together when pressed.

Using a level tablespoon of dough, drop cookies onto baking sheets prepared with baking parchment or cooking spray.

With bottom of a glass or a cup measure, gently press each dough drop evenly to about 1/4 inch high and spaced about 1" apart.

Bake for 9-11 minutes.

While cookies are cooling, make the Marshmallow Creme Frosting according to directions. (1 recipe will frost a double batch of the Better Than Oreos Cookies.)

To assemble the cookies, turn the cookies over so the flat side is facing up on half of the cookies.

With pastry bag and large piping tip or spoon, dollop frosting into center of half of the flat-side up cookies.

Gently press the tops onto the frosting to distribute it evenly, but not quite to edge of cookies.

Allow frosting to set, if you can wait that long. Otherwise pour a big glass of milk and enjoy immediately.