1. To get perfect hard-boiled eggs, place them in a saucepan and cover with cold water. Make sure the tops of the eggs are covered by at least an inch of water. Bring the water to a full boil, cover and remove from the heat. Let stand for 15 minutes. Then place the eggs in a bowl of cold water.
2. Peel the eggs and chop. Transfer to a bowl.
3. Add mustard and mayonnaise, season with garlic powder, smoked paprika and salt. Stir to combine. Taste and adjust seasonings, if necessary. Refrigerate until serving.
4. Serve on bread, topped with freshly ground black pepper and green onions.