Wash the basil, dab dry and pluck the leaves from the stems. Place the pine nuts, garlic, basil, salt and oil in a tall container and puree finely with the chopping stick. Wash and slice the tomatoes.
Cut the mozzarella into slices.
Spread 6 slices of bread with cream cheese. Spread the remaining slices of bread with the pesto. Arrange tomatoes and mozzarella on the cream cheese toast slices. Place the pesto toast slices on top. Halve the toast slices and tie them together with kitchen string.
Garnish with watercress.