Hard-boil the eggs by placing them in a pot, covering with water, bringing to a boil, then removing from heat and letting sit for 12 minutes. Transfer to an ice bath to cool.

Cut the ripe avocado in half, remove the pit, and scoop the flesh into a mixing bowl. Mash the avocado with a fork until smooth but slightly chunky.

Add the chopped hard-boiled eggs, mayonnaise, Dijon mustard, fresh lemon juice, salt, pepper, red onion, and celery to the bowl with the mashed avocado. Gently fold until well combined.

Taste the salad and adjust seasoning with more salt or pepper if needed.

Transfer the salad to a serving dish and garnish with freshly chopped parsley. Serve on its own, in lettuce wraps, or as a spread on low-carb bread.