Cut the chicken to approximately 1 by 1 inch pieces. Try to keep the sizes as uniform as possible, this helps in getting all the pieces fried evenly.
To a large mixing bowl, add chicken, salt, turmeric, red chilli powder, garam masala, ginger garlic paste, lemon juice, yogurt and finely chopped curry leaves.
Mix well and cover. Marinate for a minimum of 1 hour. You can refrigerate for upto to 36 hours.
Prepare all the ingredients to temper before frying the chicken. Pat dry the curry leaves and deseeded green chilies. Keep them aside.
To a small bowl add the crushed garlic paste, red chili powder, sugar & lemon/ vinegar/ yogurt (optional). If not using yogurt pour water. Mix together to get a thick paste. Keep this aside.
On a medium flame, heat oi in a heavy bottom deep pan for frying. While the oil heats up, add cornstarch, rice flour and egg white to the marinated chicken.
Mix well to coat the chicken well with flour and eggs or yogurt. The coating should be moist and not runny or too dry. If it is too dry, you may splash some water and mix well.
Test if the oil is hot enough by dropping a pinch of batter in the hot oil. It must come up immediately without becoming brown. If it sinks and remains there, it means the oil is not hot enough yet.
When the oil is hot enough, gently drop the chicken pieces into the oil. Do not crowd the pan.
Do not disturb the chicken pieces for 2 minutes. Stir and let them cook on a medium heat until crisp and golden. Reduce the heat slightly and let them fry the last 1 minute until deep golden & really crisp.
Remove them to a steel colander and continue to fry them in batches.
Once you are done with the chicken, reduce the flame to lowest and place 2 sprigs of curry leaves on a skimmer or strainer ladle and gently lower to the hot oil. Fry the curry leaves until crisp. Remove to the colander.
Place your slit and deseeded green chilies on the strainer ladle and lower it to the hot oil. Fry them until blistered. Turn off the heat. Toss all of these and serve this Chennai style Chicken 65 immediately or go ahead with the tempering below.
To Bake in the oven, preheat the oven to 200 C or 390 F for at least 15 mins. Place the chicken pieces on a tray lined with parchment paper or foil. Bake for 35 to 40 mins, flipping after 20 mins. When the chicken is almost done, Place the curry leaves and slit green chilies. Broil for 2 mins. Adjust the baking time as every oven is different.
Place the chicken on an air fryer parchment paper (perforated parchment paper). Air fry at 375 F or 180 C for 8 minutes, flip them and air fry for another 3 to 4 mins depending on how dry or crispy you want it. Place the sprig of curry leaves and slit green chilies and air fry for 2 more mins. Adjust the timings a bit as every air fryer is different.
Pour 2 tablespoons oil to wok. You can use fresh oil or use the same fried chicken oil. When the oil turns hot, add chopped garlic, 5 to 6 curry leaves and 2 slit green chilies. Stir fry until the curry leaves turn crisp, do not brown the garlic.
Slide the curry leaves and the chilies to a side in the wok. Lower the heat completely and pour the chilli garlic paste, 2 tablespoons water and salt. Mix well and let it cook on a medium heat until all of the water evaporates.
Taste test the fried chicken and the sauce too. Adjust your sauce to your liking, by adding more salt or red chilli to your taste.
Once it is done, you should have a thick oily chilli sauce in the wok. Add the fried chicken (set aside the previously deep fried curry leaves and green chilies for garnish).
Turn off and Toss well to coat the chicken with the tempering. Garnish chicken 65 with crunchy curry leaves and green chilies. Squeeze some lemon juice and serve with fresh cut raw onions.