Mix together the cake mix, eggs, and vegetable oil. Roll into 1½ inch balls. Place on cookie sheet and bake at 350 ℉ for 5-6 minutes.
Pull the cookie sheet out of the oven and place 4-6 mini marshmallows on each cookie - the marshmallows will just balance each cookie. Put the cookie sheet back into the oven for 2-2 ½ minutes (no longer!) When the marshmallows start to melt, they will stick to the cookie. So taking them out of the oven is much easier! The marshmallows will puff up as shown in the picture.
Let the cookies cool on the cookie sheet for a couple of minutes, then remove to wire rack to cool.
Once they are cooled completely, put frosting on top.
Frosting
Combine all frosting ingredients with hand mixer. If too thick add a little more milk. If not thick enough, add a little more powdered sugar. Frost tops of cooled cookies.
Notes
These cookies freeze great. We recommend putting them in an airtight storage container, or a thick ziplock bag, with all the air sucked out of it.