Clean and trim excess fat and skin from the drumsticks. Dry them with a clean absorbent kitchen towel. Make three to four long deep incisions.
Apply lemon juice and keep aside. Pound ginger and garlic to a paste. Hang skimmed milk yogurt for fifteen to twenty minutes to drain off excess water. Roast gram flour in a non-stick pan on low heat, stirring continuously.
Cool and mix with hung yogurt, ginger-garlic paste, turmeric powder, garam masala powder, red chilli powder, salt and green chillies.
Marinate chicken drumsticks in above mixture and refrigerate for one to two hours. Skewer marinated chicken drumsticks and roast in a moderately hot charcoal fired tandoor or alternately cook in a preheated oven at 220°C for five minutes.
Reduce oven temperature to 180°C and further cook for fifteen to twenty minutes or till completely cooked. Turn drumsticks couple of times to ensure even cooking and colour. Serve hot sprinkled with chaat masala and lemon wedges.