1. Place salmon in a food processor; pulse until finely chopped. Add cream cheese and next 4 ingredients, and process until creamy and fluffy. Add tarragon; pulse until evenly combined. Taste and adjust seasoning, if necessary. (Note: Add more half-and-half if necessary to achieve the desired texture for piping.)
2. Pipe or dollop about 1 tablespoon salmon mousse onto each cucumber slice. Garnish, if desired.
Sip: Mionetto Brut Prosecco, NV, 100% Prosecco ($14): "The fresh white peach harmonizes with the tarragon, and the hint of sweetness cuts the richness of the salmon." --Michael Velo, bubbly expert from the Carriage House Restaurant in Chicago