Bring a saucepan of salted water to the boil. Tie up the asparagus loosely with string, tips all facing the same way, and put the bundle in the pan. Reduce the heat to low and cook for 6–10 minutes, depending on the size of your asparagus. The spears should be cooked through but still retain some bite.
Meanwhile, prepare a bowl of ice-cold water and set aside. Bring another small saucep