Season the chicken with the garlic powder and black pepper.
Heat the butter in a 12-inch skillet over medium-high heat. Add the chicken and cook for 10 minutes or until it's well browned on both sides. Remove the chicken from the skillet.
Stir the stock and thyme in the skillet and heat to a boil. Stir in the rice. Reduce the heat to low. Cover and cook for 5 minutes. Stir in the peas. Return the chicken to the skillet. Cover and cook for 5 minutes or until the chicken is cooked through and the rice is tender. Sprinkle with the cheese.