Cut chicken and potatoes into bite-sized pieces.
Heat oil in a pan and sauté the chicken.
When the chicken is halfway cooked, add the potatoes and continue to stir-fry.
Add soy sauce, sugar, cooking wine, and minced garlic, then mix well.
Cover and simmer over medium-low heat until the ingredients are cooked through.
When the sauce thickens, add green onions and pepper to finish.