For the spread, place the cream cheese, goat cheese, garlic, thyme, parsley, 5 tablespoons milk, salt and pepper in the bowl of an electric mixer fitted with the paddle attachment. Beat on medium speed until well mixed. Add an additional tablespoon of milk if the spread is very thick. To make the sandwiches, spread each slice of bread with the goat cheese spread. Slice the cucumber into thin rounds and arrange on half of the bread slices. Top with the remaining bread. Press slightly, trim off the crusts and cut the sandwiches into halves, thirds or triangles. Make these sandwiches in the morning, then cover with damp paper towels and plastic wrap and refrigerate. Cut just before serving.