Mix the chicken with the cornstarch, sesame paste, salt, and Shaoxing wine and set aside for 20 minutes. Then mix the flour, sesame seeds, and white pepper in a separate bowl. Preheat the oven to 475 degrees.
Use your hands to mix the chicken and marinade until there is no standing liquid. Dredge the chicken pieces in the dry mixture, and place them on a sheet pan lined with parchment paper or nonstick foil. Bake at 475 degrees for 8 minutes on the top rack. Flip the chicken pieces and broil on low for 3 minutes until golden brown. Remove from oven.
Heat your wok to medium heat and add oil and garlic. Stir for 5 seconds, and then add the Shaoxing wine. After another 5 seconds, immediately add the chicken stock, rice wine vinegar, sugar, soy sauces, and sesame oil until everything’s at a simmer.
Gradually add the cornstarch slurry to the sauce while stirring constantly. Let simmer for 20 seconds. The sauce should be thick enough to coat a spoon. Add the chicken and scallions and toss until coated with sauce. Garnish with toasted sesame seeds and serve.