Mushroom and Barley Soup

Put the dried mushrooms in a heatproof bowl and pour the litre of just-boiled water over them.

Weigh them down with a saucer so they stay under the water.

Soak for 1 hour, until they are soft right through with no leathery core when you pinch the thickest piece.

Lift the mushrooms out and squeeze them over the bowl, then chop them roughly.

Pour the soaking liquor through a fine sieve lined with kitchen paper into a jug, and stop a good spoonful before the end.

Leave that last spoonful behind. Forest mushrooms come out of the ground with grit on them and it all settles in the bottom of the bowl, where it can stay.

Cook the pearl barley in a separate pan of unsalted water for 35-40 minutes, until swollen and tender with a slight chew.

Drain the barley and rinse off the loose starch, which would cloud the broth.

Warm the oil and butter in a large heavy pan over medium-low heat.

Cook the onion and carrot for 10 minutes, stirring now and then, until soft without colour.

Turn the heat up to medium-high and lay the sliced chestnut mushrooms in the pan in as close to a single layer as you can manage.

Leave them alone for 3-4 minutes before stirring at all.

Give them room and give them heat. Mushrooms crowded into a cool pan release water faster than it can boil away and stew grey in it, and grey stewed mushrooms never brown afterwards however long you give them.

Cook for 8-10 minutes in total, until the water they gave up has boiled away and the edges have gone deep brown.

Add the chopped soaked mushrooms and cook for 2 minutes.

Pour in the strained soaking liquor and the vegetable stock.

Add the bay leaves and the potatoes.

Simmer for 15-18 minutes, until a knife tip goes into a potato cube with no resistance.

Stir in the cooked barley and warm it through for 5 minutes.

Stir in the garlic and the cider vinegar off the heat.

The vinegar is a small amount and it matters. Dried mushrooms give a heavy, earthy pot with no acid anywhere in it, and a soup that tastes flat here almost always wants that spoonful rather than more salt.

Season with the ground peppercorns, then with fine salt.

Salt it last and taste as you go. A litre of concentrated mushroom liquor is savoury enough that it takes far less salt than the volume suggests.

Fish out the bay leaves.

Ladle into warm bowls, scatter the dill over and add a spoon of smetana to each.

Cool any left over in a shallow container, refrigerate within two hours and eat it within three days.

Expect it thicker overnight as the barley swells, and loosen it with water as you reheat.