Okroshka

Boil the potatoes whole in their skins in salted water for 18-20 minutes, until a knife tip goes to the centre with no resistance.

Drain them and leave them to cool completely before they are peeled and cut.

Boil the eggs for 9 minutes from the moment the water returns to the boil, which gives a set yolk that will crumble rather than smear.

Cool the eggs under cold running water and peel them.

Separate the yolks from the whites.

Chop the whites into 5mm dice and put them with the rest of the vegetables.

Mash the yolks in a small bowl with the mustard and the smetana until you have a smooth loose paste.

That yolk paste is the dressing and it is not optional. Egg yolk emulsifies, and it is what stops the kvass and the soured cream separating into a curdled-looking bowl within a minute of being poured.

Put the sliced spring onions in a bowl with the 5g of fine salt.

Crush them against the side of the bowl with the back of a spoon for about a minute, until they bruise, darken and go wet. Salting and crushing takes the harsh raw-onion note out, and untreated they dominate the bowl.

Peel the cold potatoes and cut them into 1cm dice.

Combine the potato, ham, cucumber, radishes, egg whites, spring onions, dill and parsley in a large bowl.

Fold the yolk dressing through until everything is lightly coated.

Cover the bowl and chill it, with the kvass alongside, for at least an hour, until both are properly cold rather than merely cool.

Divide the dressed solids between four bowls.

Pour the cold kvass over at the table, about 250ml a bowl.

Pour it at the last moment and never in advance. Cucumber and radish go limp within twenty minutes of being submerged, the radish bleeds its pink into the liquid and the whole point of the dish, which is cold crunch, is gone.

Use sour kvass rather than the sweetened bottled kind, which makes a soup that tastes of sweet bread and ham.

Whisk the kefir with the cold mineral water and use it in place of the kvass for the other standard version. Kefir on its own is too thick and too heavy to drink from a spoon.

Season each bowl with the ground peppercorns and fine salt at the table, tasting first, since the ham is already salty.

Keep the dressed solids and the kvass in separate covered containers in the fridge, below 5C/41F.

Eat the solids within a day and pour fresh kvass each time. A bowl already poured does not keep at all.