Slice chicken breast thinly into 1" pieces. Marinate in a bowl with salt, white pepper, shaoxing wine, light soy sauce, grated garlic and grated ginger.
Mince 4 cloves of garlic and 1 tbsp of ginger, and cut red bell pepper and yellow onion into 1/2" pieces. Cut pineapple into similar size chunks and set aside.
Premix sauce in a small bowl by combining sweet thai chili sauce, chicken stock, white pepper, salt, msg, and cornstarch.
In a large bowl, mix together flour, cornstarch, salt, white pepper, and baking powder. Stir until combined, then dredge chicken in the flour/cornstarch mixture until well coated, shaking off any excess.
Fry chicken at 350F in neutral oil for 3-4 minutes. Remove to let oil come back to 350F, then double fry for another 1-2 minutes. Remove and immediately season with salt.
In a pan or wok, heat 2 tbsp of neutral oil over high heat then fry garlic and ginger for 15 seconds. Add bell pepper and onions and stir fry for another 1-2 minutes to get color on the vegetables. Add pineapple and stir fry for another 30 seconds.
Add premixed sauce and stir for a few seconds until thickened. Add back your chicken and stir until combined. Serve immediately with rice and enjoy!