Combine plum sauce, soy sauce, Chinese mustard, and dark sesame oil in a large ziplock bag. Add chicken and refrigerate for at least 4 hours or overnight is even better.
Remove chicken from marinade and discard marinade.
Lightly brush or spray wings with oil
Sear over direct medium heat until well marked
Continue grilling over indirect medium heat until the meat is no longer pink at bone which should be about 10-20 minutes depending on the size of the wings.
Sprinkle with sesame seeds if so desired.
Recipe by A Camera and A Cookbook at https://acameraandacookbook.com/asian-chicken-wings/