Toss the chicken cubes with lemon juice, ginger garlic paste, and salt. Cover and marinate for 20-30 minutes at room temperature.
Whisk together the hung curd, fresh cream, cream cheese, cashew paste, white pepper, green chili paste, green cardamom powder, garam masala, cornflour, oil, and salt until smooth. Coat the chicken thoroughly in this creamy marinade. Cover and refrigerate for at least 2 hours, or overnight for best flavour.
For the charcoal smoke trick: heat the charcoal piece over a flame until red-hot. Place the small steel bowl (or a foil cup) in the centre of the marinated chicken, add the hot charcoal, drizzle with ghee, and immediately cover with a lid. Let it smoke for 8-10 minutes, then remove the charcoal and bowl.
Thread the marinated chicken cubes onto the skewers, leaving a little space between pieces so they cook evenly.
Oven method: Preheat to 240C (465F). Arrange skewers on a foil-lined tray and bake for 15-18 minutes, turning once, then broil for 2-3 minutes until charred at the edges. Grill-pan method: Cook over medium-high heat for 4-5 minutes per side until cooked through and lightly charred.
Brush the hot skewers with melted butter, rest for 2-3 minutes, then serve with mint chutney, onion rings, and lemon wedges.