Boil eggs; you can do this by placing the eggs on the stove in a pot filled with cold water, then boil them for 10 minutes when the water starts boiling, and transfer to a bowl of ice water to stop the cooking. You can also just place the eggs into a pot with already boiling water and give them about 12 minutes, then transfer to an ice bath.
Once the eggs have cooled down, peel the eggs; then chop or mash the eggs depending on how smooth you would like your egg salad.
Chop your other ingredients for the salad - celery, apple, green onion, and parsley. You can make it as fine or as coarsely chopped as you would like!
Add the chopped ingredients and the eggs to a bowl along with the mayonnaise, sour cream, curry powder, garlic powder, mustard, lemon juice, and salt and pepper. Mix together well.
Taste and adjust for seasonings - you can add more salt and pepper if needed, or more lemon juice, just bearing in mind that the more liquid you add, the runnier the egg salad will be.
Serve on bread - sandwich bread, rye bread, or crisp bread are all great options! Save in an airtight container and keep in the fridge for 3-4 days.