Place the eggs in a large saucepan and pour over enough cold water to cover the eggs by about 1/2-inch. Set the pan over high heat and bring to a boil. Cover the pan with a lid and remove it from the heat. Let the eggs stand covered for 15 minutes.

Drain and transfer the eggs to a large bowl of ice water. Let the eggs sit in the ice water for 10 minutes.

Drain the eggs from the ice water. Refrigerate the eggs for at least 15 minutes.

Peel and halve the eggs lengthwise. Transfer the yolks to a bowl. Chop the whites into small pieces and set aside.

Mash the yolks with a fork until crumbly. Add the mayonnaise, mustard, 1/2 teaspoon salt, and 1/4 teaspoon black pepper and stir until smooth and creamy.

Fold in the chopped egg whites, green onion, and celery. Season to taste with salt and black pepper.

Serve the egg salad as a sandwich, wrap, stuffed into tomatoes or bell peppers, or spooned over a bed of lettuce.