Grind peppercorns in a spice/ coffee grinder or mini chopper. It's alright if they are a little coarse. It's not necessary to grind it into a fine powder.
Add ginger and garlic and process into a coarse powder.
Add turmeric, chile powder, salt and 2/3 cups water and process until smooth in a food processor or mini chopper.
In a pot, combine chicken with contents of chopper. Add 1/3 cup water. Bring to a boil. Reduce to a simmer and let the chicken cook on medium-low heat for 30 minutes.
In a deep skillet or pot, heat oil. Add curry leaves. Fry for 1 minute. Add cumin seed and fry for another minute.
Add onions and cook on low heat for 10 minutes, until golden brown.
Add chicken with its sauce into this pot and cook on medium high heat for 15 minutes.