Whisk soy sauce, mirin, sake, honey, grated ginger, and minced garlic together until honey fully dissolves. Set aside.
Pat chicken thighs completely dry with paper towels. Season with salt and white pepper.
Heat oil in a large skillet over medium-high heat until shimmering. Add chicken smooth side down. Cook 5 to 6 minutes without moving until deep golden brown.
Flip and cook 4 to 5 more minutes until the internal temperature reaches 75°C (165°F). Transfer chicken to a plate.
Reduce heat to medium-low. Pour sauce into the same pan and scrape up the browned bits. Simmer 2 to 3 minutes, stirring occasionally, until slightly reduced.
If sauce is still thin, stir in the cornstarch slurry and cook 30 to 60 seconds until glossy and thick.
Return chicken to the pan. Spoon sauce over each piece and cook 1 minute over low heat, turning once.
Remove from heat. Rest 3 minutes. Slice or serve whole over steamed rice. Top with sesame seeds and spring onions.