Soak 10-15 Kashmiri red chilies in water for 15 minutes.
In a blender or food processor, combine 1/2 teaspoon cumin seeds, 1 teaspoon coriander seeds, 1 teaspoon sesame seeds, 3 cloves, 6 peppercorns, 3 cardamoms, 1/2 inch peeled chopped ginger, 4 chopped garlic cloves, and 3/4 cup chopped red onion with the soaked chilies.
Puree the mixture to a smooth paste, adding a little water if necessary.
Heat 1/3 cup oil in a pot, and when hot, add the spice paste and 1-inch cinnamon stick.
Fry the mixture for 5 minutes.
Add 1 1/2 - 2 cups of chicken to the pot and fry for another 5 minutes.
Remove the cinnamon stick.
Add 2 chopped tomatoes and 1 teaspoon salt, then fry for 5 more minutes.
Pour in 2 1/2 cups of coconut milk and let it simmer until the chicken is almost cooked.
Add 1 teaspoon of rice vinegar and 1/2 teaspoon of garam masala.
Taste for salt and adjust if needed. If the curry is too spicy, add some peeled cubed potatoes. The sauce can be diluted with 1/2 - 3/4 cup water if desired.