In a medium skillet or saute pan combine the turmeric, chili flakes, cumin seeds, coriander seeds, cloves, ginger, garlic powder, mustard seeds, pepper, allspice, and cinnamon and cook, shaking the pan frequently, until spices are fragrant and just beginning to smoke. Remove from the heat, transfer to a shallow plate and allow to cool completely. Transfer to a coffee grinder or spice mill and process until very finely ground. Reserve 6 tablespoons of the spice mixture separately and transfer the remainder to an airtight container and save for another purpose.
In a mixing bowl combine the chicken, 2 tablespoons of the curry powder, 1 teaspoon of the salt and 2 tablespoons of the vegetable oil and set aside, covered, for 20 minutes.
In a large Dutch oven, heat the remaining 2 tablespoons vegetable oil, and, when hot, add the chicken pieces and cook, turning occasionally, until golden brown on all sides, about 8 minutes. Add the onion, garlic, ginger, thyme, hot pepper if using, and remaining 4 tablespoons curry powder and cook, stirring, until the vegetables are soft, about 4 minutes. Add the chicken broth, coconut milk, and brown sugar and bring to a simmer. Add the remaining teaspoon of salt, and cook, stirring occasionally, until chicken is very tender and falling from the bone and the sauce has reduced enough to coat the back of a spoon, about 1 1/2 hours. Stir in the cilantro and adjust seasoning, if necessary.
(Note: traditionally, curried chicken roti is eaten with the chicken still on the bones. If you prefer otherwise, at this point you can remove the chicken from the sauce and remove the meat from the bones and then return the meat to the sauce before serving.)
Serve the chicken and sauce ladled into the center of the roti breads, then fold both sides over the filling. Fold the top and bottom ends over the sides to form a neat square package, and serve.
West Indian Bread for Roti:
Yield:6 large roti breads
To make the breads, combine the flour, baking powder and salt in a mixing bowl and make a well in the center. Combine the oil and water and add this mixture to the well. Using your hands, mix to form a dough. Knead for about 5 minutes, or until the dough is smooth. Divide the mixture into 6 balls of dough and set aside for about 2 hours, covered with a damp kitchen towel. On a lightly floured surface, roll each ball of dough into a thin, flattened circle about 9 inches in diameter. Set aside, covered, until ready to cook the breads to serve. (Do not stack.)
Heat a large griddle or 12-inch skillet over high heat and add 2 teaspoons of vegetable oil. When hot, add the bread dough and cook until brown spots form on the bottom, about 1 minute. Turn the bread and cook on the second side, about 1 minute longer. Transfer to a large plate or baking sheet and cover with a damp towel to keep warm while you prepare the remaining breads.