In a large bowl, add the chopped onion, cilantro, garlic, mint, ginger, serrano, coriander, salt, cumin, both chile powders, turmeric, and garam masala; stir until well combined. Add the lamb and use your hands to mix well, pounding and smashing the meat between your hands to thoroughly incorporate the seasonings. Cover and refrigerate until well chilled, at least 1 hour.

Meanwhile, soak ten 8-inch bamboo skewers in cold water for at least 30 minutes.

When ready to cook the kebabs, preheat a grill to high (about 450°F) or a grill pan over very high heat. Drain the skewers and shake off any excess water. Retrieve the lamb mixture and divide into 10 evenly sized portions (about 5 ounces each). Roll the portions into tight balls; working with one ball at a time, thread onto a skewer. Starting from the tip of the skewer, work the mixture up, gently rolling the kebab between your palms so that it is an even thickness from end to end, with a slightly flattened, ribbed sausage shape, about 1 inch thick. Repeat with the remaining balls an 9 skewers.

Once the grill is hot, add the kebabs, spacing about 1 inch apart. Close the grill or tent the grill pan loosely with foil, and cook until the meat is charred on one side and loosens easily from the grates, about 2 minutes. Open the grill or remove the foil, turn the kebabs, and continue cooking with the grill open until charred on the opposite side, about 2 minutes. Baste the kebabs liberally with ghee and continue cooking until the meat is cooked through, 1–2 minutes more. Transfer to a platter and serve immediately, with thinly sliced onion, naan, lime wedges, and chutney.