'Christmas Pudding' which was her second novel is by far the best of the early ones though, with a bitter cynicism running through it that gives the perfect acid bite to act as an antidote to all the Christmas cheer and those feel good adverts that seem to exist only to highlight how imperfect most of our lives are.
Amongst the froth and fun is an unflinching look at a group of bright young things at their least bright and young (in the death grip of a New Year's Day hangover). To provide just such a hangover, and to celebrate the bitter edge I recommend a Pink Gin, which I suppose is best described as a very dry martini. It's gin with a couple of drops of Angostura bitters, shaken well over ice and strained into a cocktail glass.
It's a no nonsense, single minded, kind of a cocktail, designed for potency rather than frivolity. It perfectly matches the brittle, bitter, edge to Mitford's writing where an ingrained sense of superiority excuses really appalling behaviour.
I would recommend a gin like Martin Millers for this kind of thing, it's smooth enough to drink on its own, but with a traditional juniper driven flavour profile, so no unique selling point botanicals to mess with the flavour profile of the cocktail. Angostura is both aromatic and bitter (as the name suggests) a bottle goes a long way but is a useful thing to have around for all sorts of drinks, and other culinary purposes. Even better would be something like The Bitter Truth's Travellers set (which I would really like, and have been meaning to buy for an age). There aren't many times when it makes more sense to buy miniatures rather than full size bottles, but this is one of them, and bitters are the perfect way to invigorate otherwise dull drinks.
There is also Fever Tree's Aromatic tonic water which uses Angostura bark, it will give you the more sensible long version of a pink gin, or if you want to go entirely alcohol free, tastes grown up enough (aromatically, and pleasingly, bitter) on its own to all but forget there's no gin involved.