Boil the eggs. Place eggs in a pot, cover with water, and bring to a rolling boil. Turn off the heat, cover, and let sit for 10–12 minutes.
Transfer to an ice bath for 5 minutes, then peel.
Prep the avocado base. In a mixing bowl, mash the avocado with lemon or lime juice, Dijon, and a pinch of salt and pepper. Keep it slightly chunky for texture, or mash it smooth if you prefer.
Chop the eggs. Dice the peeled eggs into small pieces. For a creamier feel, you can grate them using the large holes of a box grater.
Combine. Add the eggs to the avocado mixture.
Stir in the onion, herbs, and any optional add-ins. If using mayonnaise, fold it in now for extra richness.
Taste and adjust. Add more lemon or lime juice for brightness, more salt for balance, and black pepper for a little bite. If it feels too thick, a teaspoon of water can loosen it.
Serve. Spoon onto toast, tuck into a sandwich, wrap in a tortilla, or scoop into lettuce cups.
Sprinkle with extra herbs or a pinch of paprika if you like.