Preheat oven to 180 Degrees C (350 F)
Use a sharp knife to remove the crusts from 12 slices of bread. Using a rolling pin, roll each bread slice to flatten as thinly as possible. Using a 6cm/2 ½” round cookie cutter, cut 2 rounds from each slice.
Brush the bread rounds on both sides with olive oil or spray each side with olive oil. Firmly press the bread rounds into two 12-hole patty tins.
Bake for 12-15 minutes, turning pans halfway through cooking, until the cases are lightly browned.Remove from oven and transfer to wire racks to cool completely.
Combine mayonnaise, sour cream, prepared horseradish, dill and black pepper in a small bowl. Adjust seasoning to taste, adding more horseradish, pepper or dill as required.
Cut smoked salmon slices into 2 ½ cm/1” wide x 5 cm/2” strips. Arrange folds of salmon in each bread case.
Spoon about a teaspoon of cream mixture onto the salmon. Serve topped with a sprig of dill and a couple of baby capers, if using.
Serve as soon as possible after assembling.