Place eggs in a large pot and add cold water to cover. Put flame to high heat and boil hard for one minute. Remove pot from heat, cover, and set aside for 15 minutes. Meanwhile, mince and mix mayonnaise with dry mustard in a small bowl, breaking apart any lumps. Add onion and salt and set aside. After 15 minutes, remove eggs to a bowl of ice-water for a few minutes. Peel eggs under running water. Allow the eggs to cool completely before slicing in half, wiping the knife occasionally to prevent sticking. Mash yolks in a large bowl and add mayonnaise mixture. Don't mix too much, just until incorporated and fluffy. Spoon yolk mixture into egg whites and place on platter. Cover and chill. Just before serving, sprinkle with fresh herbs.