Slice the cucumbers into about 1/4 inch (6 mm) thick slices.
If you'd like, cut each slice with a cookie cutter that is just slightly smaller than your slice, as shown in my picture. This is just to make the dish prettier.
Alternatively, slice the cucumber lengthwise with a potato peeler in paper thin slices. Roll the slices with one end folded under the roll (so that the filling will stay in place).
Cut about 3/4 of the salmon (3 oz) in really small pieces. Reserve the rest to decorate the top (cut in thin slices).
In a bowl, add the salmon with the ricotta cheese, the lemon juice, Dijon mustard, salt and pepper to taste. Mix with a spoon.
Whip the whipping cream to soft peaks. Fold into the salmon mixture. Spoon the mixture into a piping bag, with a large tip. I used the Wilton 1M. And pipe some of the mixture on top of the cucumber slices (or into the cucumber rolls).
Top with a little slice of salmon and a few pieces of chives.
Store in the refrigerator until ready to serve.