This recipe from AllRecipes.com is rated 4.5/5 stars.  I simplified it by stir-frying just the chicken meat and onion with the seasonings.

RECIPE : ONION CHICKEN STIR FRY
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1 piece chicken breast, about 250g, diced
1/2 onion, sliced thinly
2 tablespoons peanut oil
1/2 cup water
1 tablespoons soy sauce
1 tablespoon sugar
1 tablespoon cornstarch
1 stalk spring onion , for garnish (optional)

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01. Mix water, soy sauce, sugar and cornstarch well in a small bowl, set aside.

02. In a heated wok, add peanut oil.  Once the oil starts to smoke, add onion slices, and fry till they turn translucent.

03. Add chicken meat, and continue to fry till they turn white.

04. Stir the bowl of sauce to mix well again (cornstarch will settle to the bottom when set aside) and pour into the wok.

05. Keep stirring till the sauce is reduced and thickened to coat the chicken meat.

06. Transfer onto a plate, garnish with spring onions, and serve immediately with steamed white rice.