Bring a pot of water to a boil. While the water boils, prepare an ice bath in a bowl for your eggs.
Boil 12 eggs for 10 minutes. While they boil, chop up the leaves of a bunch of watercress until you have 1/4 cup.
After 10 minutes, immediately transfer your eggs to the ice bath to stop the eggs from overcooking.
Peel your hard-boiled eggs.
Cut the eggs in half and separate the yolks from the whites.
Roughly chop up the egg whites and add all the yolks into a large bowl.
Add 1/2 tsp onion powder, 1/2 tsp kosher salt, 1/4 tsp white pepper, and 1/4 cup mayonnaise to the same bowl and mix together.
Mix until everything is combined, leaving you with a yellow yolk paste.
Add in the roughly chopped egg whites and mix to combine.
Add 1/4 cup watercress, the juice of 1/2 lemon, and 10 good cranks of black pepper.
Mix everything to combine and taste to see if it needs any additional seasoning. You may want to add more mayo if you prefer a creamier consistency.
Serve on toast, in a sandwich, or with crackers.