How to Make It
In a medium bowl, whisk together cream cheese, milk, horseradish, lemon zest and juice. Gently fold in trout, chopped scallions and dill. Season lightly with pepper. (Spread can be made 1 day ahead; cover and refrigerate. Let sit at room temperature for 30 minutes before serving.)
Spread 1 tsp. trout mixture over each cucumber round. Garnish with sliced scallions and lemon zest, if desired, and serve.