The first thing you learn when you make marshmallows from scratch is that Ghostbusters was lying to you. That is not how marshmallow goop behaves. (They used shaving cream.) Actual marshmallow goop is far more insidious, more inexorable, more sticky than the deceptively benign horrors that our comedic but intrepid heroes faced back in 1984.
That said, the payoff of working with marshmallow goop is well worth the effort:
I'd be posting a recipe right now, but at this point I'd just be plagiarizing Alton Brown's excellent instructions. I'll get back to you later, once I've had the chance to perfect a few wacky flavors.
These cocoa marshmallows were made exactly according to Alton's recipe, except I only made 1/3rd of the recipe (which fit perfectly in a bread pan) and added 1 tablespoon of cocoa powder to the 'mallow batter in addition to the vanilla (having turned the beater speed down first and up again afterwards to prevent splatter), plus another 2 teaspoons of cocoa powder to the cornstarch/powdered sugar coating mixture.
Of course, s'mores had to happen immediately.
The only potential downside here is that now I want to make marshmallows in all the flavors. Like banana, and espresso, and Nutella, and whiskey, and caramel, and chai, and Earl Grey. It'll be the tastiest pain in the ass there ever has been.