1 lb Smoked cod 1/2 lb Onions 1/2 lb Shelled peas 10 fl Milk * 1 oz Flour 1 t Dry mustard 1 oz Butter 2 lb Mashed potato * (or substitute 5 oz milk and 5 oz cream) . Chop onions roughly and fry in butter until tender. Remove from heat an stir in flour and mustard. Add milk. Return to heat and stir until thickened. Add cod, cut into 1/2-inch cubes, and peas. Turn into ovenproof dish and cover with mashed potatoes. Bake in a moderate oven at 400F/200C, for 35-45 minutes, or until golden brown. . (Though not traditional, the addition of 2-3 oz of cheddar cheese to the sauce makes this an extremely tasty dish.)