For the marinade, mix together all the marinade ingredients (yoghurt, ginger, garlic, salt, chilli, garam masala, lemon juice, gram flour, cumin powder, cardamom, oil) in a bowl and add the paneer, onion and peppers. Cover with cling film and allow the paneer and vegetables to marinate for 30-40 minutes, or longer, in the fridge.
Preheat the Retigo combi oven to 250C, on hot air 50% and put a Retigo express grill GN container to the combi oven to preheat.
Thread the vegetables and paneer alternately onto the skewers. Reduce the temperature to 220C and grill in the oven for 7 minutes, drizzle over the melted butter, turn and cook for another 2 minutes or until charred at the edges.
Sprinkle with chaat masala and serve.