Celeriac and ham hock gratin

1. Preheat the oven to 220˚C, gas mark 7. Grease a 22cm x 30cm (about 2 litres) baking dish. In a large pan, bring the stock and cider to the boil. Add the celeriac to the pan; cook rapidly for 3 minutes, then add the potatoes. Simmer briskly, covered, for 12-15 minutes, until the vegetables are softened, but not falling apart.

2. Drain the veg, reserving about 100ml of liquid. Heat the butter in the pan, add the flour and cook for 1 minute. Off the heat, gradually add the liquid, whisking until smooth. Return to the heat; bubble for 2-3 minutes, whisking constantly until thickened slightly. Spoon ¹⁄ ³ of the veg mixture into the dish. Season; scatter with ¹⁄ ³ of the ham. Top with another layer of veg and another ¹⁄ ³ of the ham, cover with foil and bake for 10 minutes.

3. Mix the remaining ham with the breadcrumbs, gruyère and a little black pepper. Remove the foil, scatter the breadcrumb mix over the top and bake for 20-25 minutes, until the breadcrumbs are golden and the ham is crispy. Serve with the mustard and green salad.