Den na Kiselo Mlyako
Kiselo mlyako is not yogurt, it is a national treasure containing Lactobacillus bulgaricus, a bacterium discovered by a Bulgarian and named after Bulgaria itself. Every Bulgarian abroad has tried to explain why their yogurt is different, and every Bulgarian abroad has wept at the foreign substitutes. The bacteria are literally Bulgarian. You cannot argue with science or with a homesick Bulgarian in a supermarket aisle.