Carefully scoop the yolks into a bowl, try not to break the white of the egg.
In the bowl, add your yellow mustard, mayonnaise, salt, pepper. Using a fork break up the yolks and stir the ingredients until evenly distributed. Add in any additional add-ins (optional). Taste and season with more salt and pepper if necessary.
Scoop or pipe the yolk mixture back into the egg white shell. Top with any garnishes (optional). Enjoy!