As many hardboiled eggs as you'd like cut in half. If you'd like 12 deviled eggs, then make 7 or 8 hard boiled eggs. One or two always turn out ugly as they're being shelled. The whites of the ugly ones get slipped to the dogs.
Sweet pickle relish
Cut eggs in half. Slip yolks into a bowl. Mash yolks with a fork until fine. add a half to a teaspoon of dry mustard or how ever hot you want it to be. Add a spoon of pickle relish. Add enough mayonnaise to make it creamy or desire consistency. Spoon yolk mixture into the white of the egg. Sprinkle with paprika for color or add an olive slice or a sweet gerkin slice or some dill or parsley for color.