Spray a large heavy skillet with cooking spray. Heat the skillet on medium high heat and add the chicken drumsticks to the pan. Brown the chicken on the outside for around 10 minutes or until the skin starts to become crispy. Meanwhile mix balsamic vinegar, soy sauce, honey and garlic in a small bowl. Once the chicken has browned on all sides add the mixture and reduce heat to low and cover skillet with a lid. Cook for at least 20 minutes or until the chicken has cooked throughly. Take lid off of the pan and turn the heat to high for around 5-8 minutes to reduce and thicken the sauce. The sauce will start to boil and become thicker and thicker. Make sure to cut off the heat before the sauce starts to burn. Take the chicken out onto a serving dish and pour the sauce on top. Sprinkle sesame seeds and chopped chives on top.