Trim 500g of leeks, discarding the roots and the tips of the leaves, then slice each leek into thick coins. Wash them thoroughly in a colander under cold running water. Melt the butter in a deep-sided pan and add the leeks. Cover with a piece of greaseproof paper and a lid and let them steam for about 20 minutes on a low heat, until soft.
Slice 6 pieces of thick bread and toast them lightly. Place them on a baking sheet or grill pan. Warm the overhead grill. Sprinkle 1 heaped tbsp of plain flour over the leeks, stir and continue cooking for a couple of minutes. Stir in 250ml of double cream, 2 tbsp of mild grain mustard and 150g of coarsely grated caerphilly, a little salt and plenty of black pepper. I like to stir in a handful of chopped parsley, too, if there’s some around.
Once the cream is hot and the mixture has started to bubble, stir in a drained 400g can of butter beans and continue cooking for a couple of minutes.
Spoon the mixture on to the pieces of toast and place under the heated grill. Watch carefully and let cook until golden. Serves 2
The leeks shouldn’t colour. A layer of greaseproof or cooking parchment placed on top of the leeks, then covered by a lid, will encourage them to cook in their own steam so they finish tender and buttery, but without colour. They will be soft and juicy that way. An occasional stir will help.
Tarragon is the herb to use if you want to gild the lily. Its aniseed notes are good with the cheese and the beans. Consider, too, the addition of a pinch of caraway seeds if you have them.