Rassolnik

Put the beef in a large pan with the 2.5 litres of cold water.

Bring it up slowly over about 20 minutes, until the first bubbles break the surface.

Skim the grey foam off as it gathers, and keep skimming until the surface stays clear.

Add the bay leaves and the whole peppercorns.

Simmer with the lid ajar for 2 hours, until the meat gives under a fork.

Cook the pearl barley in a separate small pan of unsalted water for 35-40 minutes, until the grains have swollen, split along the seam and are tender with a slight chew left.

Cook the barley in plain water in its own pan, and never in the soup. Brine stops a grain softening altogether, and barley put into the pot with the cucumbers stays hard however long the pan goes on.

Drain the barley and rinse it briefly under hot water to wash off the loose surface starch, which would otherwise turn the soup cloudy and faintly gluey.

Warm the oil in a frying pan over medium-low heat.

Cook the onion and carrot for 8-10 minutes, stirring now and then, until soft with no colour.

Add the grated cucumbers and cook for 5 minutes, until the water they release has gone and they smell of pickle rather than of raw brine.

Lift the beef out and strain the broth into a clean pan.

Shred the meat off the bone with two forks and discard the fat and gristle.

Bring the strained broth to a simmer and add the potatoes.

Cook for 12-15 minutes, until a knife tip slides into a cube with no resistance.

Get the potatoes fully soft before anything sour arrives, for the same reason as the barley. A chalky potato in a sour broth is the commonest fault in this soup and there is no fixing it in the pan.

Stir in the cooked barley, the cucumber mixture and the shredded meat.

Simmer for 10 minutes, until the broth has taken on the smell of the pickles.

Bring the cucumber brine to the boil in a small pan on its own, then take it straight off the heat.

Boiling the brine separately takes the raw edge off it and, more usefully, lets you add it by degrees instead of committing the whole jar at once.

Add the hot brine to the soup a ladleful at a time, tasting between each one, until it is sour enough to make you sit up.

Stop while you still want a little more. Brines vary enormously in salt and acid, and once the pot has gone too sour there is nothing to correct it with but water.

Season with the ground peppercorns, then with fine salt only if it needs it.

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 much thicker the next day, since the barley goes on drinking overnight, and loosen it with water as you reheat.