Just a quick, slightly hungover update: Nigella's "Date Steak" sauce from Kitchen is awesome and so easy to make. All you have to do is mix quantities of vinegar, mustard, soy sauce, sugar, ginger and some kind of berry jelly (I used the cranberry sauce I made for Christmas) in a pan until everything gets bubbly and then remove from the heat to cool. We ate this with steak, mashed potatoes and salad leaves and the sauce went just as well with the mash and lettuce as the steak, to my surprise.
Date Steak Sauce