Heat the oil in a frying pan over low heat, then add the garlic. Stir and fry for a minute or two until the garlic goes a shade darker. Add the curry leaves, stir, then add both type of chillies and fry for a few seconds.
Add the chilli powder and fry for a few seconds, stirring continuously as it will tend to burn. Be careful of getting the fumes in your eyes or nose. Now add the tomato puree and fry for a minute or so.
Add the yoghurt. Fry for another minute, then turn off the heat. Taste the sauce, season and adjust the flavourings. I find that adding a bit of mayo here gives a bit of body to the sauce and gives a wonderful coating.
Add the chicken and gently toss to coat. Garnish with coriander leaves.