First, prepare the spread.
In a medium bowl, thoroughly mix the strained Greek yogurt and room-temperature goat cheese until smooth.
Stir in the chopped watercress, grated carrots, chives, and a pinch of sea salt until everything is well combined.
Assemble the sandwiches. Generously spread the goat cheese mixture on one side of each slice of bread.
Arrange the thinly sliced cucumber in a single, even layer on half of the bread slices.
Place the remaining bread slices on top, spread-side down, to close the sandwiches.
Using a sharp serrated knife, carefully cut the crusts off all four sides.
Cut each sandwich in half diagonally, and then in half again to create four classic triangular tea sandwiches.
Arrange them closely together on a serving platter and enjoy immediately.
Don't toss those crusts!
Brush them with a little olive oil, sprinkle with herbs, and toast them in the oven for delicious, crunchy croutons.