Preheat oven to 180°C.
Mix contents of KNORR Chicken a'la King Dry Cook-in-Sauce with milk in a jug then transfer to a small saucepan.
Bring to the boil and stir until thickened then stir in the wholegrain mustard.
Arrange skinless chicken fillets in an ovenproof dish and pour the sauce over.
Top with a good sprinkling of breadcrumbs and rosemary.
Bake at 180°C for 35-40 minutes until golden brown and cooked through.
Serve with steamed mixed vegetables.