Okroshka

Kvass is the older version and gives a malty sour taste; kefir with sparkling water is milder and creamier, and became common in Soviet times. For this recipe's 1.2 litres of liquid, use 750 ml plain unsweetened kefir and 450 ml cold sparkling mineral water, a ratio of 5 to 3. Mix the two just before pouring, so the fizz stays. Another cold kefir soup, with beets, is cold beet soup.

Look for live bread kvass, naturally fermented and sold in the fridge, not a sweet canned soda drink; too much sugar overwhelms the vegetables. Check the label: the less sweet, the better for a soup. You can make your own: homemade bread kvass needs one to two days of fermentation, so start two days before you want to serve the soup. Chill it well before use.

Yes to both. Doctor's sausage or good boiled ham, 250 g, is a classic substitute and needs no cooking; dice it like the beef. For a vegetarian okroshka, leave the meat out and add 2 more hard-boiled eggs and another 100 g of cucumber so the soup is not thin. Keep the sour cream and mustard, which carry much of the flavour.

Salted, dressed okroshka releases water from the cucumbers and radishes and goes thin and sour within hours. Prepare the chopped mix without salt and keep it covered in the fridge for a day or two, and keep the cold kvass in a separate bottle. Combine and salt only when serving, and dress only the portions you will eat. Leftover dressed soup is best eaten the same day.

None is strictly required, but they make the soup richer. The traditional dressing mashes hard-boiled yolks with mustard, and sometimes horseradish, then thins it with a little kvass before the rest is added. Use 2 yolks and 1 teaspoon of Dijon mustard for this recipe. Put 1 tablespoon of sour cream into each bowl at the table; a spoonful is enough to make the soup creamier without hiding the kvass.