Using a 1 ¾-inch fluted round cutter, cut 8 rounds from frozen bread slices, discarding scraps. To prevent bread from drying out during assembly, cover with damp paper towels, or store in a resealable plastic bag, and let thaw at room temperature.
In a small bowl, stir together cream cheese, tarragon, vinegar, salt, and pepper until creamy. Transfer mixture to a piping bag fitted with a large star tip (Wilton #1). Pipe upright dollops of cream cheese mixture onto thawed bread rounds.
Place 5 or 6 folded radish slices on top of each bread round, arranging to resemble a flower. Serve immediately, or place in a container, lightly covered with damp paper towels, and refrigerate for up to an hour.
Just before serving, garnish with tarragon leaves and ground pink peppercorns, if desired.
Recipe by TeaTime Magazine at https://teatimemagazine.com/champagne-tarragon-radish-flower-canapes/