I doubled everything except the butter (per the reviews) and this turned out wonderfully. Magical, even. It was excellent on deep, dark chocolate cupcakes.. and also on popcorn! Like kettle corn, but creamy. Highly recommended for all your sweet and salty frosting needs.
Note: Make this before you make your cupcakes/cake/etc as it really benefits from some extra setting-up time in the fridge. Just be sure to leave time for it to return to room temperature afterward.