Sweet Potato Gratin

This recipe, which I believe originated from the excellent Food for Friends restaurant in Brighton, is a favourite with my family. It is helpful to use a food processor with a slicing blade to cut up the potatoes, but after that the rest is easy. As with the Celeriac Terrine, we like it served with our favourite red pepper sauce, along with a rocket (arugula) salad, which also offers a contrasting texture.