Bring 1 inch of water to a boil under a steamer basket. Add shrimp, cover and steam for 4 to 6 minutes, turning once, until opaque and the thickest shrimp reach 145°F.
Spread shrimp in a shallow container, cool for 5 minutes and refrigerate promptly for 30 minutes until cold. Blot away any collected liquid and chop the shrimp very finely.
Stir crème fraîche, horseradish, dill, lemon juice, salt and pepper together. Fold in chopped cold shrimp until lightly bound.
Butter one face of every bread slice. Divide shrimp filling evenly among eight slices, spread to the corners and close with the remaining bread, buttered faces inward.
Trim crusts and cut each sandwich into three fingers to make 24 pieces. Serve two per portion, keeping covered and refrigerated until serving the same day.