Heat the oil in a large skillet, and brown the chicken thighs at a medium-high setting.
Once browned, remove the chicken and set aside for now. Drain all but about 3 tablespoons of oil from the skillet, but leave any brown bits that you can at the bottom of the pan.
Add the cinnamon bark to the hot oil and saute for about 30 seconds.
Next comes the ginger and garlic, stirring and cooking for another 30 seconds.
Add the chillies to the mix for another 30 seconds.
Sprinkle in the cumin, salt, and Cayenne pepper, then the chopped cilantro. Continue to cook at a medium setting for about another minute.
Add the lemon juice and zest and chicken stock to the skillet. Cook for another minute, until heated thoroughly.
Return the chicken thighs, and any juices on the plate, to the pan, and simmer until the meat is thoroughly cooked, or about 20 minutes.