1.Make pickled onion by combining onion, vinegar, sugar and salt in a small bowl.
2.Combine mustard, juice and cream in small bowl.
3.Discard skin and bones from trout; flake flesh into medium bowl.
4.Spread each slice of bread with mustard mixture; cut each slice into 6 squares.
5.Top each square with trout, drained pickled onion and a sprig of dill. Serve immediately. pickled onion Place ingredients in screw-top jar; shake well. Refrigerate several hours or overnight.
A whole smoked rainbow trout will give you enough flesh for this recipe. Smoked salmon can be used in place of trout. 24 hours before: Skin, bone and flake trout. Prepare pickled onion. Make sour cream spread; cover, refrigerate. 1 hour before: Assemble ready to serve.