Rinse the asparagus and cook in food steamer for 5 minutes. When done, place on a plate.
Prepare the sauce. Separate the egg white from the egg yolk. Set aside the egg white (we will use it later). Mix the egg yolk with the yogurt, the mustard and the chives. Season with salt and pepper.
Whisk the egg white until stiff. To do this, add a pinch of salt to the egg white, and mix with an electric mixer, always in the same direction, gradually increasing speed, until stiff.
Then, gently add the stiff egg white to your yogurt mixture, and mix, slowly and carefully, so as to not break the egg white. This is your sauce.
Place the sauce in a small bowl next to your asparagus. Enjoy by dipping the lukewarm asparagus in the cold sauce.