Apple and Onion Gratin

This is very good with roast pork, duck and venison, the Bramleys as usual providing the basis for that satisfying tension between sweet and tart, with the onions offering a savoury counterpoint. You could add a herb like marjoram or sage if you like, but I prefer the simplicity of this dish, the crunchy crumb topping reacting well with the soft mixture underneath.