We'll be making marshmallows flavored like a popular drink in the US (it has a name offensive to readers in the UK so I've removed it): it's a "stunt drink" where you drop a shot of Irish Cream and Whiskey into a glass of Guinness. In the cocktail version, it foams up, and you have to chug it before it makes a mess! Sort of immature, but hey, it's a fun drink, and makes a tasty marshmallow.
This recipe can be made with any beer, or any liqueur. The ingredients are fairly cheap, so you can make it over and over again to practice. I've made several batches where the liqueur choice was... challenging. Absinthe marshmallows seemed like a good idea at the time, but ended up being inedible (the second version was a absinthe/vanilla cognac blend, which was more palatable).
You may have heard that baking is chemistry... well, candymaking is ESPECIALLY chemistry. That is, the quantities of ingredients, the order they are added, the ingredients' temperatures, and timing of the steps are all important.
To this end, I originally was going to try to do this the "real" way, that is, how a candy kitchen might make marshmallow, but it ended up being way too crazy. Ah well.
So this recipe is basically adapted from Jessica's recipe at How Sweet It Is - not as fancy as the "real" industrial way, but very yummy, and much much easier.
Safety warning: candy is hot. We're going to be boiling sugar, which is basically napalm. If it gets on your skin it will burn you and stick to your skin. It is real painful and will make an ugly scar. I've never met a professional candy man who didn't have a ton of scars on his arms. This is a relatively safe recipe, so don't be scared... but definitely be careful.