To make the marinade, mix Soy Sauce (2 teaspoon), Worcestershire Sauce (2 teaspoon), Ketchup (1 tablespoon), and Brown Sugar (2 teaspoon) in a small bowl.
Pour marinade over the Boneless, Skinless Chicken Thigh (4 piece) and gently massage it into the chicken.
Let the chicken marinade in the fridge for at least 2 hours and up to overnight.
Grill or pan-fry the chicken over medium-high heat for about 2 minutes on each side or until fully cooked. Set aside.
In a small bowl, mix Soy Sauce (1 teaspoon), Worcestershire Sauce (1 teaspoon), Brown Sugar (1 teaspoon), Ground Black Pepper (1/2 teaspoon), Salt (1/4 teaspoon), and Corn Starch (1 teaspoon).
Melt Butter (1 tablespoon) in a pan over medium-low heat, then add Olive Oil (2 teaspoon).
Add Onion (1/2) and Garlic (2 clove). Saute until the onions are soft and translucent.
Add the black pepper sauce mixture, then turn up the heat. Let the sauce simmer for just a minute. This will allow it to thicken up.
Pour the sauce over the chicken, then serve right away. Enjoy!