Fish pie

Preheat the oven to 180 ºC (350 ºF). Grease an ovenproof dish with margarine.
Cook the macaroni in sufficient boiling salted water until just soft. Drain and rinse under hot running water. Set aside.
Melt the butter in a pan, add the cake flour and cook, stirring continuously. Remove from the heat.
Drain the asparagus and pour the liquid into a measuring jug. Add sufficient milk to the liquid to make up 300 ml.
Slowly, add the milk mixture to the butter mixture, stirring continuously.
Season to taste with salt, pepper and mustard powder.
Add the asparagus pieces, fish, macaroni and half the Cheddar cheese and mix.
Turn into the prepared oven dish and sprinkle the remaining Cheddar cheese on top.
Bake for 30 to 35 minutes or until heated through and the cheese has melted.