Chicken & mushroom Hotpot

Chicken
British
Chicken & mushroom Hotpot
Butter50g
Onion1 chopped
Mushrooms100g
Plain Flour40g
Chicken Stock Cube1
Nutmegpinch
Mustard Powderpinch
Chicken250g
Sweetcorn2 Handfuls
Potatoes2 large
Butter1 knob