The old town is well stocked with traditional Bulgarian mehanas — restaurants in the style of village taverns, typically occupying the ground floors and courtyards of National Revival houses. They serve the Bulgarian classics: kavarma (slow-cooked meat in a clay pot), kebapche (grilled minced meat cylinders), shopska salata (tomato, cucumber, and white cheese), and tarator (cold yoghurt soup with cucumber and walnuts).
Quality varies considerably — some have fallen into tourist-trap territory with inflated prices and generic menus. The ones with handwritten menus and a local clientele at lunch are usually the better bet. In summer, most have garden seating in the cobbled courtyards, which is where you want to be in the evening.