Preheat oven to 350 degrees
Beat the butter until smooth. Mix in the egg. Add the hot cocoa liquid, oil, and vanilla. Mix well.
Add the cake mix slowly. Mix well after each addition.
Stir in chocolate chips and mini marshmallows.
Scoop a tablespoon of dough and place on a baking sheet that has been lined with parchment paper. Add 3 marshmallows to the center of the cookie.
Bake for 6-7 minutes. Try to not OVER BAKE the cookies.