Ingredients (Serves 4—6)
2 tbsp plain flour
1/2 tsp salt
1/4 tsp freshly ground black pepper
1/2 tsp mustard powder
500ml/16fl oz whole milk
450g/1lb fresh asparagus
1) Start by making a white sauce. Melt the butter in a saucepan over a low heat. Gradually blend in the flour, salt, pepper and mustard powder, stirring until it starts to come away from the sides of the pan. Warm the milk and gradually add to the roux, stirring constantly, until the mixture thickens and begins to bubble. Remove from the heat and put to one side.
2) Wash the asparagus and break off any woody ends. Cut into 1cm/1/2in pieces and cook for 5 minutes in a small amount of boiling water. Drain, reserving the cooking liquid.
3) Put the asparagus in a blender and process until smooth.
4) Add boiling water to the asparagus cooking water until you have 250ml/8fl oz, then add the water and the pureed asparagus to the white sauce in the other saucepan.
5) Check the seasoning then heat thoroughly