White Chicken Casserole

Makes is an amazing side to any Christmas dinners and would also be one of the best ways to use up leftover turkey or meats from any roasts. This herby cheesy American style casserole is a great one pot dish that will feed everybody. It takes some time but the flavour is deep.
For the chicken braise:
700g skinless chicken breast
1 fat clove of garlic, skin on and crushed
1 bay leaf
1/2 tsp rosemary
1 tsp sage
1 tsp flakey sea salt