Trim any excess fat from the chicken thighs. In a bowl, combine the chicken with oyster sauce, dark soy sauce, Shaoxing wine (or mirin), sugar, chicken bouillon, black pepper, and baking soda. Mix thoroughly and let it marinate for at least 15 minutes.
In a small saucepan, heat ½ tbsp cooking oil over medium heat. Add the minced garlic and sauté until fragrant (about 30 seconds). Stir in ¼ cup water, soy sauce, 2 tbsp oyster sauce, 1½ tbsp sugar or honey, and 1 tbsp Shaoxing wine. Bring the mixture to a boil, then reduce heat and simmer for 2–3 minutes.
In a separate small bowl, mix the cornstarch and 1 tbsp water to form a slurry. Add the slurry to the sauce and stir immediately as it thickens. Remove from heat and set aside.
Heat your Blackstone Griddle over medium heat and drizzle with cooking oil. Place the marinated chicken on the griddle. Optional: add a splash of water and cover with a cooking dome to steam. Cook for 4–6 minutes on each side, or until the chicken is fully cooked and has a golden brown char.
Slice the cooked chicken into 1-inch thick pieces. Serve over steamed white rice if desired. Drizzle with the prepared sauce and garnish with sesame seeds and thinly sliced scallions.
