The name comes from the Hungarian 'láng', flame: lángos was originally baked at the mouth of the bread oven before deep-frying took over.
A yeasted potato dough is stretched thin and deep-fried until puffed and golden, then rubbed with garlic and topped with sour cream and shredded cheese. Vienna's Naschmarkt and street festivals sell it hot, folded into paper for eating on the move.