Preheat oven to 350. Prepare an eight inch square pan with cooking spray; set aside. In a mixing bowl, combine cookie mix, egg, and water. Mix thoroughly blended. Divide cookie dough in half. Press half the dough evenly into bottom of pan. Bake for ten minutes. Cool. Arrange the nine chocolate pieces (see notes) into three rows of three pieces each. Place spoonfuls of marshmallow cream on top of chocolate. Spreading to cover chocolate and cookie dough. Roll remaining cookie dough into a 8 "x 8" sheet large enough to cover the marshmallow cream. Carefully place the sheet of dough over the marshmallow cream. You may need to cut the sheet of dough into smaller pieces to make it easier to transfer into the baking pan. Bake for 35 minutes, or until light golden brown. Cool completely. Cut into two inch squares.

If you are using a seven ounce chocolate bar, cut out five squares of chocolate and then cut each square in half. You only need nine of the ten pieces. For other size chocolate bars, you need to use a piece of chocolate about the size of a Hershey's Kiss (approximately 1/4 ounce).