• Melt the butter in a saucepan.
• When the butter has just foamed, remove it from the burner and add the flour and salt off the heat.
• When it is stirred together, it should form a soft roux. This means that you should be able to draw a line through the mixture and it will not all flow back. If it does, then you need to add a tiny bit of flour.
  
• While still off the stove, add a little bit of the milk and stir. You will see that it looks a little thicker; add a little more milk, stir, and then put it back on the burner. Continue to add the milk gradually, stirring all the while. When it comes to a boil (bubbles breaking the surface), let it cook for another minute. Depending on what you are using it for, you might like to add white pepper, or if aesthetics don't matter, a nice grinding of black pepper. If all you're after is a white sauce, you're done!
  

Cheese Sauce

• If you are making a cheese sauce, the mustard added to the white sauce will add depth to the flavour of the cheese. Then add the cheese, give it a little mix, and then take it off the heat and cover it. In about five minutes, the cheese will have melted.