Clean and trim excess fat and skin from the drumsticks. Dry them with a clean and absorbent kitchen towel. Make three to four long deep incisions.
Apply lemon juice and keep aside. Peel ginger and garlic, wash and grind them to a paste. Wash green chillies, remove stem and chop finely. Hang skimmed milk yogurt for fifteen to twenty minutes to drain off excess water.
Roast gram flour in a microwave bowl on Microwave LOW (50%) for five minutes stirring twice in between. Cool and mix with hung yogurt, ginger and garlic paste, turmeric powder, garam masala powder, red chilli powder, salt and chopped green chillies.
Marinate chicken drumsticks in above mixture and refrigerate for one to two hours. Preheat Convection oven to 220°C. Place marinated chicken drumsticks on a flat dish and roast for five minutes in the preheated oven.
Reduce oven temperature to Convection 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.