Potato, Leek and White Bean Bake

What the potato slices need

This bake is all about a simple balance of textures: potatoes that turn soft and creamy, leek that gently cooks until sweet, firm white beans and a crisp topping. Mustard gives the cream sauce a little kick and gentle sharpness without overpowering the mild flavour of the vegetables. The apple cider vinegar salad cuts through the richness. The result is a fresh counterpoint without needing much else.

Cut the potatoes into slices about three millimetres thick. Even thickness matters more here than perfectly round slices: thicker pieces may take longer to cook while the thin ones fall apart. Briefly parboiling them makes the cooking more predictable and means the sauce doesn’t have to bake for ages before the potatoes are done. Let them steam-dry for a moment after draining; excess water will thin the cream sauce. A mandoline is quick, but a sharp knife and care to cut evenly work just as well.

Leek often has dirt between its layers. So first slice it into rings and rinse them in a large bowl of cold water; lift the leek out and leave the grit behind at the bottom. Gently cooking the rings in butter makes them soft and sweet without browning. For convenience, use canned or jarred beans and rinse them so the liquid from the packaging doesn’t affect the sauce. Cannellini beans are creamy, but large lima beans or ordinary white beans work too.

The sauce is intentionally light: cream is combined with milk and seasoned with mustard, salt and black pepper. Dijon mustard gives it a distinct, refined sharpness; a milder mustard makes the result gentler. For a plant-based version, you can use unsweetened cooking cream and replace the butter with olive oil. Choose breadcrumbs that aren’t too fine so they bake up crisp on top. Panko gives you larger, airy crumbs; coarse fresh breadcrumbs brown nicely too.

Serve the bake after letting it rest briefly, with a salad of crisp leaves and, if you like, thinly sliced apple, dressed with apple cider vinegar and olive oil. The apple is optional, but it goes well with the fresh dressing. Cover and refrigerate leftovers within two hours, and eat them within three days. Reheat in an oven dish until piping hot all the way through; cover loosely if the breadcrumbs brown too quickly. The crust will be less crisp after storing, but the oven will bring back some of its texture.