Prepare the Chicken:

Start by coating the chicken pieces with cornstarch, salt, and a dash of white pepper. This creates a light crust that will help absorb the sauce and give the chicken a delightful texture.

Cook the Chicken:

Warm a good amount of oil in a spacious skillet or wok over medium-high heat. When the oil is shimmering, add the chicken pieces in small batches, making sure not to fill the pan too much. Sauté until the chicken turns a lovely golden brown and is fully cooked, which should take around 5-7 minutes. Transfer the chicken to a plate lined with paper towels to absorb any excess oil.

Sauté the Vegetables:

In the same skillet, pour off any extra oil, leaving about a tablespoon behind. Add the chopped bell peppers and chives, and sauté for 2-3 minutes until they are slightly tender but still crisp.

Make the Sauce:

In a small bowl, combine ketchup, chili sauce, oyster sauce, and sugar. Mix well until the sugar is dissolved.

Combine and Serve:

Add the cooked chicken back into the skillet with the sautéed vegetables. Pour the prepared sauce over the chicken and vegetables. Stir well to coat everything evenly. Allow it to simmer for an additional 2-3 minutes, letting the flavors meld together.

Garnish and Serve:

Transfer the sweet and spicy chicken to a serving dish. Garnish with additional chives if desired.