Mix the flour and ground coriander together in a large bowl. Trim the lamb of excess fat and cut into 2-inch pieces and add to the flour and toss well to coat. Heat the oil in a large, heavy-bottomed pot and when it is hot, add the lamb pieces and begin to brown on all sides. Reserve the browned meat in a bowl and drain off the excess fat. Add the onion, garlic, and ginger to the pot and cook until softened and caramelized. Add the cumin seeds, garam masala, tomato paste, chile, and chocolate chips, and stir well. Add the tomatoes, red pepper, reserved meat, red wine, salt, pepper, and then add enough water to just cover the meat. Season with salt, and pepper, and cook for about 2 hours over medium-low heat, until the meat is very tender and the sauce is thick.