A pungent, tangy North Indian specialty infused with robust pickling spices, mustard seeds, fenugreek, nigella seeds, and fresh green chillies.
Toss the chicken with lemon juice and salt; rest 20 minutes.
Stir together yogurt, achari masala, kalonji, ginger-garlic paste, and Kashmiri chili powder; coat the chicken and refrigerate 4 hours.
Thread the cubes onto skewers, leaving small gaps.
Cook over high charcoal heat or under a hot grill, basting with mustard oil and turning.
Grill until the edges char and the chicken is cooked through.
Serve hot with onion rings, lemon wedges, and mint chutney.