Marinate the chicken with the marinade ingredients for 8 hours, preferably overnight.
Mix all of the spice paste ingredients together. Set aside.
Heat up cooking oil in a large sauce pan over medium heat. Add the mustard seeds, fenugreek seeds, and curry leaves. Sizzle in the oil for 30 seconds.
Add in the shallots. Cook down for 20 minutes until brown.
Add in the ginger garlic paste and cook for 1 minute.
Add the spice paste to the pan and cook for 30 seconds.
Add in the chopped tomatoes. Fry for 5 minutes. Mash with the back of a spoon.
Stir in the marinated chicken. Fry for 8 minutes, making sure th chicken is evenly coated. Season with the white wine vinegar, sugar, and salt. Cook for 2 more minutes.
Pour in the water. Cover and simmer for 20 minutes.
Season with the fennel powder and black pepper. Simmer for another 5 minutes. Turn off the heat and let rest.
Heat up 1 tbsp of coconut oil in a small sauté pan over medium high heat. Once the oil is hot, turn off the heat and add in the curry leaves, birds eye chilies, and grated coconut. Let the ingredients infuse in the oil for 30 seconds.
Pour the tempering oil over the curry.