Cut chicken into bite-sized pieces. Mix with 1/2 cup cornstarch, flour, baking soda, salt, pepper, and smoked paprika. Add cold water to cover and let sit for 10 minutes.

Drain excess water. Heat oil in a pan. Fry chicken pieces until golden and cooked through. Set aside.

In the same pan, sauté onion, yellow bell pepper, and red bell pepper until they wither and become tender.

In a bowl, mix ketchup, soy sauce, oyster sauce, vinegar, sugar, 1 tsp cornstarch, and 1/4 cup water.

Pour sauce into the pan with the vegetables. Stir and cook until thickened.

Add fried chicken back to the pan. Toss to coat evenly with sauce.