Only a quail egg is tiny enough to fit atop this canape. It is deviled, dressed with caviar and dill, and affixed to a round of pumpernickel with a silky misture of creme fraiche and Dijon mustard.
Prepare an ice-water bath; set aside. Place quail eggs in a medium saucepan, and cover with several inches of cold water. Cover pan; bring to a boil over high heat. Turn off heat, and let sit 2 minutes, stirring several times to ensure even cooking. Use a slotted spoon to transfer eggs to ice-water bath. Let cool completely, about 5 minutes. Remove eggs one at a time; pat dry with paper towels. Peel, and place in a medium bowl. Cover with plastic wrap; refrigerate until ready to use, up to 6 hours.
Preheat oven to 300 degrees. Using a 1 1/8-inch round cookie cutter, cut out 4 rounds from each bread slice. Arrange rounds in a single layer on baking sheets, and bake, turning once, until dried out and lightly toasted, about 10 minutes. Let cool on a wire rack.
Combine creme fraiche and mustard in a small bowl. Cut eggs in half lengthwise; gently remove yolks. In a small bowl, mash yolks with a fork until completely smooth. Stir in 2 tablespoons creme-fraiche mixture, and season with salt and pepper. Transfer to a pastry bag fitted with an Ateco number 27 star tip, and pipe into empty egg halves.
Spread a small amount of remaining creme-fraiche mixture on each bread round. Place an egg on top of each; add some caviar, and garnish with a sprig of dill. Serve immediately.