Peel and roughly chop the onions. Warm the butter and oil in a deep saucepan over a moderate heat, then add the onions and cook till soft. Scrub and finely dice the carrots, and finely dice the celery, then add to the softening onion and continue cooking for ten minutes or so till tender.

Warm the milk in a small saucepan and set aside. Stir the flour into the vegetables and continue cooking for two or three minutes, then add the milk and stir to a thick sauce. Pour in the vegetable stock and cider, bringing it to the boil, then lowering the heat and letting the mixture simmer for a few minutes. Stir in the mustard and check the seasoning. (It may want pepper, but probably very little salt.)

Grate the cheese and stir into the soup, leaving it to simmer (it is crucial it doesn’t boil) for five minutes, until the soup has thickened. Add a handful of parsley as you bring it to the table and serve with bread.

I suggest a mature, full-flavoured Cheddar such as Keen's or Montgomery here. The stock should, if possible, be home-made, chicken or vegetable. Bread is pretty much non-negotiable here, either torn and placed in the base of the soup bowl, the soup ladled over it, or toasted and dipped into the soup's creamy depths in fat, jagged chunks.

From Greenfeast: Autumn, Winter, by Nigel Slater, published by 4th Estate Books. Photographs: Jonathan Lovekin