To Make the Egg Salad:

1. Add the eggs to a large saucepan and cover with water.
2. Bring to a full boil then turn off the heat and allow to sit in the hot water for 10 minutes.
3. After 10 minutes drain the hot water and cover the eggs with cold water and allow to cool for 10 minutes.
4. Crack the eggs and peel while submerged in the cool water to make them easier to peel.
5. Dry the eggs and set aside.
6. Repeat with all the eggs, then finely chop and add to a mixing bowl.
7. Add the mayonnaise, watercress, salt and pepper to the eggs and mix well.

To Assemble Sandwiches:

1. Butter evenly all of the bread slices and lay them out in an assembly line.
2. Spread an even amount of the egg salad onto the brown bread slices and top with a slice of brown bread.
3. Spread an even layer of cucumber slices onto the buttered white bread slices, slightly overlapping them. Sprinkle with dill, salt and pepper and top each with a slice of white bread.
4. Cut the crusts off all the sandwiches and cut them into triangles and rectangles.