Slice eggs in half, and scoop egg yolks into a bowl. Set aside egg whites for the time being.
To the egg yolks, add dijon mustard and mayonnaise. Mash with a fork until well-combined. Add salt and pepper to taste. Add mixture to a piping bag or a ziploc bag with the corner cut out. Pipe the mixture into the egg whites.
Top with paprika and green onions, if desired. Serve right away, or store in an air-tight container in the fridge for 2-3 days.
Nutrition Facts (per four deviled eggs, recipe makes 16): 205 calories, 17 g fat, 1 g total carbs, 0 g fiber (1 g net carbs), 13 g protein