In a medium bowl, whisk together honey, soy sauce, rice vinegar, minced garlic, grated ginger, cornstarch, sesame oil, red pepper flakes (if using), and black pepper.
Add chicken breasts to the marinade; cover and refrigerate for at least 30 minutes (up to 4 hours for deeper flavor).
Heat vegetable oil in a skillet over medium-high heat until shimmering.
Add marinated chicken breasts and cook for about 5-7 minutes per side until golden brown and the internal temperature reaches 165°F (74°C). Baste occasionally with leftover marinade.
Once cooked, let the chicken rest before slicing. Simmer any remaining marinade in the skillet until thickened.
Serve sliced chicken with the glaze poured over it.