Combine 1 cup frosting and 2 cups powdered sugar in mixing bowl.
Stir frosting and powdered sugar together, slowly adding more powdered sugar (up to 3 cups total) until dough begins to form.
When the dough becomes too thick to stir with a spoon, finish kneading by hand. Stop adding powdered sugar when dough no longer sticks to hands.
Video
Notes
While technically edible, this ice cream play dough is not meant to be eaten as a meal - but rather a non-toxic play dough alternative. Always supervise children.