Butter Kulcha is the Punjabi leavened flatbread in its plainest, most generous form: a plain kulcha brushed with a heavy hand of butter the moment it comes off the heat. There is no stuffing and no masala worked into the dough, so it lives or dies on the bread itself and the butter that soaks into it. It sits a step away from richer stuffed and seasoned versions, defined precisely by what it leaves out.
A kulcha is a soft leavened dough, raised with a little yogurt and a rising agent, rolled into a round and baked until it puffs and takes brown blistered spots. The butter is the whole point of this version: as the bread comes off the heat, while it is still hot and pliable, it is brushed liberally so the fat melts in rather than sitting on top. Good execution shows in the bread first, soft and slightly chewy with an airy crumb and real char from the heat, not a pale dense disc. The butter should be generous and absorbed, leaving the surface glossy and the bread enriched, not a greasy slick pooling on a tight crust. Sloppy versions are underproofed and tough, or baked so hard they crack instead of folding, or finished with a thin mean brush that never reaches the edges, or so heavily greased on an overbaked bread that it just sits wet on top.
The variations branch off quickly into their own territory. Amritsari kulcha, stuffed with spiced potato and crisped till flaky, and masala or onion kulcha worked through with seasoning, are distinct enough that each deserves its own article rather than being crowded in here. Within the plain buttered version the levers are small: a sprinkle of coriander or nigella seed pressed into the dough before baking, a slightly richer dough, or an even heavier finish of butter for the table. It is usually eaten alongside chole or a similar curry, where its job is to carry sauce. Judged on its own, a good butter kulcha is soft, charred, airy bread carrying a real layer of melted butter; a poor one is dense or cracked bread with a thin or greasy finish.