Using a stand or hand mixer, mix cookie ingredients together in a large mixing bowl until well combined.
Use a spoon to scoop out small amounts of dough to roll into 1/2 inch spheres. Place the dough balls onto a lightly greased cookie sheet. Press down on the dough balls to slightly flatten.
Bake the cookies at 375 degrees for about 8 minutes. The amount of baking time will depend entirely upon the size of the cookies. Watch closely! Take them out as soon as they get a hint of brown.
Let the cookies stand on the cookie sheet for 2-3 minutes after baking. Remove from cookie sheet and let cool on a wire rack for another 10 minutes.
Refrigerate baked cookies for about 20 minutes.
Meanwhile, melt the chocolate chips and butter together in the microwave. Melt for 10-15 seconds at a time, remove, stir, and continue until the chocolate is completely melted. Let stand 30 minutes until chocolate thickens to a spreadable consistency.
When cookies and chocolate are ready, heat the marshmallow cream in the microwave for about 10 seconds. This will make it easier to spread.
Spread marshmallow cream on one cookie, chocolate on the other and sandwich together. Repeat until all cookies are used.
These cookies should be stored in the fridge or another cool place. A warm room will cause the marshmallow cream and chocolate to soften and the cookies could melt apart.