Peel and place hard boiled eggs in a large bowl. Use a pastry blender to chop the eggs. For tea sandwiches, chop the eggs into smaller pieces.
Add mayonnaise, dry mustard, salt, pepper and green onions and mix well. Check seasoning.
Spread each slice of bread with butter. Spread the egg salad on 3 slices of bread. Top with remaining slices of bread. For tea sandwiches, trim crusts and cut each sandwich into thirds. For a regular sandwich, add lettuce if desired.