In a mixing bowl, combine the softened cream cheese, chopped dill, chives, lemon juice, salt, and pepper. Mix until smooth and well blended.

Using a sharp knife or a mandoline, thinly slice the cucumber. Pat the slices dry with a paper towel to remove excess moisture.

Lay out the slices of bread on a clean surface. If desired, lightly spread butter on one side of each slice. Spread a generous layer of the herb cream cheese mixture onto the unbuttered side of each slice. Arrange the cucumber slices evenly over the cream cheese on half of the bread slices. Top with the remaining slices of bread, cream cheese side down.

Using a sharp knife, carefully trim the crusts off the sandwiches for a clean, elegant look. Cut each sandwich into quarters or halves, depending on your preference. Arrange them on a serving platter and garnish with additional fresh dill or chives if desired.