In a pot, place the 6 large eggs and cover them with cold water. Bring the water to a rolling boil over medium-high heat. Once boiling, cover the pot, remove it from heat, and let it sit for 10-12 minutes to hard-boil the eggs.
Transfer the cooked eggs to a bowl of ice water. Let them cool for at least 5 minutes. Gently tap each egg on a hard surface and peel off the shell. Rinse the eggs under cold water to remove any shell pieces.
In a mixing bowl, use a fork to mash the peeled eggs until your desired consistency, chunky or smooth. Add mayonnaise, Dijon mustard, olive oil, lemon juice and zest, paprika, garlic powder, salt, and pepper. Mix well to combine.
Fold in the finely diced celery, chopped green onions, parsley, and dill if using. Stir gently until all ingredients are evenly distributed. Taste and adjust seasoning with additional salt and pepper as needed.
Spread softened butter on slices of your favorite bread if desired. Add a generous scoop of the egg salad mixture and top with fresh lettuce. Place another slice of bread on top to complete your sandwich.
Cut sandwiches in half for easy eating. Serve immediately or refrigerate until ready to serve. Enjoy your delightful egg salad sandwiches with a side of chips or a light salad!