Place the eggs in a medium saucepan and cover them with cold water, ensuring the water level is about 1 inch above the eggs.

Heat the pan over medium-high heat until the water starts to boil. Once boiling, lower the heat to a gentle simmer and cook the eggs for 10 minutes.

Remove the eggs from the saucepan and transfer them to a bowl of ice water to cool for 5 minutes. This will make peeling easier and stop the cooking process.

Peel the eggs by gently tapping them on a hard surface and rolling them to loosen the shell. Rinse the eggs to remove any remaining shell pieces.

Chop the boiled eggs into small pieces or roughly mash them with a fork in a mixing bowl.

Add the mayonnaise, mustard (if using), salt, and black pepper to the bowl. Mix well until the eggs are evenly coated and creamy.

Taste and adjust seasoning if needed. Optionally, garnish with freshly chopped parsley or chives.

Serve immediately as a sandwich filling, on crackers, or on toast, or refrigerate for later use.