Chicken Casserole With Broccoli without sauce

2 teaspoons olive oil 1 kg skinless chicken thigh , trimmed of fat and cut in half 1 large brown onion, finely sliced 2 stalks celery , chopped 2 teaspoons[...]

4 chicken breasts , diced 1 (12 ounce) jar chicken gravy 1 (10 ounce) can Campbell's chicken soup 10 small potatoes , quartered 6 carrots , chopped 1 onion ,[...]