As a vegetarian, one of my mainstays in Russia has been khachapuri. Although khachapuri is a Georgian dish, it is extremely popular throughout Russia and can be found at both roadside food stands and in fancy restaurants.
Authentic Georgian khachapuri is a little like a pizza or the Turkish pide. Even within Georgia there is some variation, but khachapuri is typically a round of leavened bread filled like a pizza (or in some cases like a calzone, with bread on top) with a mound of mouth-watering cheese. Some Georgian versions also include melted butter and/or a raw egg. All are served hot so that the cheese is stringy and soft.
In Russia, there are even more versions of this delicacy. It seems that Russians and other ethnic groups have adopted the idea of khachapuri but modified it to fit their desires. For example, although traditional khachapuri is about the size of a plate, most khachapuri sold at roadside food stands is smaller: about the size of the somsa or pirozhki sold along side it. Oftentimes it is filled with a variety of cheeses, sometimes the slightly sweet tvorog.
At Central Asian food stands that specialize in somsa (meat-filled Central Asian pastries), khachapuri is sometimes made with unleavened, flaky dough so that it is similar to a somsa. While on a trip to Yaroslavl, I even had khachapuri with cheese and mayonnaise!