Pepper Chicken

2 tablespoons vegetable oil
1 pound boneless, skinless chicken breasts, cut into 1-inch pieces
1/2 cup ketchup
3 tablespoons light soy sauce
1/8 teaspoon black pepper
2 tablespoons all-purpose flour
1 large onion, halved and cut into thin slices
2 green peppers, seeded, cored and cut into thin slices
1 can (4 ounce) sliced mushrooms, drained
Cooked white rice for serving

1. Heat oil in a large nonstick skillet over medium-high heat. Add chicken; cook for 5 minutes, stirring occasionally.
2.In a medium-size bowl, whisk 1 cup water, ketchup, soy sauce and pepper; gradually whisk in the flour.
3. Remove chicken from skillet. Stir in the water-ketchup mixture and bring to a boil; add chicken and the onion. Reduce heat to a simmer and cook, covered, for 20 minutes, stirring occasionally.
4. Add peppers and mushrooms and simmer, covered, for 15 more minutes, stirring occasionally. Serve with rice.