Creamy Chicken with tenders

1 teaspoon vegetable oil 12 ounces boneless skinless chicken breasts , cubed 1 onion , chopped 2 garlic cloves , minced 1/2 teaspoon black pepper 2[...]

2 teaspoons mustard , any flavor 2 teaspoons low-fat mayonnaise 2 tablespoons nonfat sour cream 1 teaspoon lemon juice 4 ounces boneless skinless chicken[...]

1 (3 lb) whole chickens , rinsed (or 3 lb. skinless chicken thighs) 2 stalks celery , including leafy green tops, cut into large chunks 1 large onion , halved[...]