Cut all eggs directly in half (vertically). Be careful not to tear egg whites when cutting
Carefully pull out the yolks and place them in a small mixing bowl
Set aside 12 egg whites on an egg tray. Clean up any spare yolk on egg whites with a toothpick
Mash up eggs yolks until they are very fine (no lumps)
Add mayonnaise to yolks gradually
Then add both types of mustard, onions, and finally black pepper
Mix well (spatula recommended) and form a medium to thick filling for egg whites
Use a tiny spoon or pastry bag to neatly fill egg whites with yolk (fill eggs so there are no gaps between whites and yolks)
Once all 12 eggs are filled, garnish with cilantro according to preference
For added security (to hold eggs in place on a tray) insert one toothpick down the middle of each egg
Use as much mayonnaise and mustard according to personal preference (for a thicker or more loose filling). Toothpicks may be used to clean off any excess yolks for final presentation.