Chicken casserole with dumplings

Name: Chicken casserole with dumplings
Prep time: 20 min
Cook time: 1 h
Total time: 1 h 20 min
Cuisine: European, British
Ingredients: 4 medium Chicken breast, skinless, raw cut into large chunks; 190 g White Self Raising Flour 150g, plus 2 tablespoon; 4 spray(s) Calorie controlled cooking spray; 1 medium Onion(s) finely chopped; 3 medium Carrots, raw sliced into 5mm rounds; 1 stick(s) Celery, Raw finely sliced; 460 g Potato(es), Raw roughly chopped; 2 clove(s) Garlic crushed; 0.5 tablespoons, level Dijon Mustard; 1 cube(s) Chicken stock cube(s) to make 850ml stock; 2 sprig(s) Rosemary, Fresh; 2 sprig(s) Thyme, Fresh; 1 leaf/leaves Bay leaf, dry; 1 tablespoons, level Cornflour; 120 g Fat Free Natural Yogurt; 6 teaspoons Tarragon, fresh finely chopped, plus extra, to serve; 4 portion(s), medium Green Beans