Using a 2½-inch round cutter, cut 24 circles from frozen bread slices, discarding scraps. Let thaw for 5 minutes.
Brush both sides of bread circles with melted butter. Place on a rimmed baking sheet. Place another rimmed baking sheet on top of prepared bread to flatten bread.
Bake until lightly browned, 6 to 8 minutes. Let cool.
In a mixing bowl, combine fontina cheese, sour cream, cream cheese, and rosemary. Beat at medium speed with a mixer until well combined. Spread a thin layer of cheese mixture on top of each bread round. Divide turkey among prepared bread rounds. Top each with a cucumber slice and a radish slice.
Transfer remaining cheese mixture to a pastry bag fitted with a medium star tip. Pipe a rosette of cheese mixture onto each radish slice.
Garnish each canapé with a parsley leaf, if desired.
Recipe by TeaTime Magazine at https://teatimemagazine.com/smoked-turkey-fontina-canapes-recipe/