Make a smooth paste out of mint leaves, coriander leaves, green chilies, ginger, garlic along with little water. Keep the green paste aside.
Now marinate the cleaned chicken pieces add yogurt, 4-5 Tablespoons of that green paste, all of the spice powder, some salt, mustard oil and lemon juice. Mix everything very well and keep them in refrigerator for overnight or at least 5 hours.
Take out the chicken from refrigerator and let it come to room temperature.
Heat a charcoal on open flame, then place a steel bowl or alumunium foil in the bowl. Place the hot charcoal in the bowl or foil and pour 1 Tablespoon of oil over the charcoal. There will be smoke, immediately cover the bowl for 4-5 minutes.
After that remove the charcoal and bowl.
In the mean time soak few bamboo skewers in water for 10 minutes.
Now arrange the chicken pieces in the skewers.
Preheat your oven in highest temperature.
Place the chicken skewers in a oven proof tray.
Bake them in highest temperature for 20 minutes. Then take them out, apply some melted butter all over them, turn them to the other side and bake them for another 15 minutes.
For more charred flavor, broil them for 3-4 minutes on high.
If you are cooking on stove top then heat 2 - 3 Tablespoons of oil in flat pan.
Place 2 - 3 skewers, and cook on medium flame for 15 minutes, turn them to the other side, cook on high flame for another 15 minutes or until the chicken cooks thoroughly.
Sprinkle some chat masala all over them and serve hot.