Sour cabbage leaves
Whole white cabbage leaves fermented in brine, soft and pliable, with a sharp sour and salty taste.
Whole white cabbage leaves, or whole heads, fermented in brine like sauerkraut, which leaves them supple enough to roll without tearing. They are sold in Turkish, Balkan and Eastern European shops, in jars, vacuum packs or, in winter, as whole heads.
Substitute:
Fresh white cabbage leaves, briefly blanched with the thick rib trimmed, roll just as well but bring no sourness. Layering sauerkraut with a little of its brine in the pot makes up for part of that, though not for the full, matured fermented flavour.