Cheesy gratin of leeks and brussels sprouts

Method

1. To make the buttered crumbs, melt the butter in a pan and stir in the breadcrumbs. Remove from the heat immediately and allow to cool. Use what you need and store the remainder in a box in the fridge to scatter over gratins or fish pies.

2. Trim most of the green part off the leeks (use to make soup or pop into the stock pot). Leave the white parts whole, slit the top and wash well under cold running water. Cook in a little boiling salted water in a covered saucepan until just tender, 15 minutes approx.

3. Meanwhile, put the cold milk into a saucepan with a few slices of carrot and onion, 3 or 4 peppercorns and a sprig of thyme or parsley. Bring to the boil, simmer for 5 minutes, remove from the heat and leave to infuse for 10 minutes. Strain out the vegetables, bring the milk back to the boil, and thicken with roux to a light coating consistency. Add the mustard and two-thirds of the grated cheese, keep the remainder of the cheese for grating over the top. Season with salt and freshly-ground pepper: taste and correct the seasoning if necessary.

4. Drain the leeks well, slice into chunks, mix with the blanched Brussel sprouts. Arrange in an ovenproof serving dish, season well, coat with the sauce and sprinkle with grated cheese mixed with a few buttered crumbs. Reheat in a moderate oven 180˚C until golden and bubbly – about 15 minutes.