Step 1 In the container of a blender, combine the egg yolks, mustard, lemon juice, and hot pepper sauce. Cover and blend for about 5 seconds.
Step 2 Place the butter in a glass measuring cup. Heat butter in the microwave for about 1 minute, or until completely melted and hot. Set the blender on high speed and pour the butter into the egg yolk mixture in a thin stream. It should thicken almost immediately. Keep the sauce warm until serving by placing the blender container in a pan of hot tap water.
