With a knife or scissors, cut the skin and tendon around the base of chicken drumette. Holding the exposed bone of the drumette, gently push the meat all the way down the opposite end, forming a knob of meat like a "lollipop". Repeat with remaining drumettes.
In a bowl, combine plum sauce, calamansi or lemon juice, soy sauce, honey, rice vinegar, chili oil, ginger, garlic, red chili flakes, salt, and pepper. Whisk together until well-blended.
Add frenched drumettes to plum sauce mixture and marinate in the refrigerator for at least 4 hours or overnight for best results.
Drain chicken, reserving marinade. Wrap the exposed bone of each drummette with a strip of aluminum foil.
In a saucepan over medium heat, bring marinade to a boil for about 5 minutes or until completely heated and reduced.
On a lightly greased baking sheet, arrange chicken in a single layer. Bake in a 350 F oven, basting every 10 minutes with marinade, for about 30 to 35 minutes or until browned and thermometer inserted in the thickest part of the meat reads 165 F.
Remove from oven and sprinkle with sesame seeds. Serve hot.