The combination of slippery, soft and silky leeks in a thyme-flavoured, creamy sauce with chunks of roast chicken piping hot under a crisp, golden carapace is heaven indeed. I served it with carrots roasted while the gratin cooked and peas but whatever veg you fancy will go with this. Or serve it on its own. Lovely.
Serves 2, generously
Prep: 25 min
Cook: 45 min
1 onion
40g butter
½ tbsp vegetable oil
400g trimmed leeks
few sprigs thyme
1 heaped tbsp flour
150ml white wine
150ml chicken or vegetable stock
splash of milk
300g leftover roast chicken
3 tbsp finely grated Parmesan
3 tbsp fine breadcrumbs
Halve, peel and finely chop the onion. Melt the butter in the oil and stir in the onion with a generous pinch salt. Adjust the heat so the onion softens without browning, stirring often until slippery soft. Meanwhile, slice the leeks in 1 cm rings. Agitate in a bowl of water to loosen any grit then drain. Strip the thyme leaves from the stalks and chop. Stir the leeks into the softened almost cooked onion. Cover and cook for 5 minutes, stir, re-cover and cook for a further 5 minutes or until the leeks is floppy and tender. Sift the flour over the top of the leeks and stir briskly to disperse. Stir in the white wine, stirring constantly before adding the stock. Keep stirring, letting it bubble up to make a thick sauce. Add a little milk, stirring steadily, adjusting the heat as necessary, so everything cooks gently. Fold in chunks of chicken then tip the mixture into a gratin dish – mine was 30 x 16 x 6cm. Gently flatten the mix and leave to cool. Mix cheese and breadcrumbs and scatter over the top. Bake now or later, the dish placed on a roasting sheet to catch any spillage, at 200C/gas mark 6 for about 30 minutes, checking after 20, until the top is crusty and golden.