Step #1 Reserving some small sprigs of dill for garnishing the crostini, in a bowl, dill, mix the mustard, sugar & capers until they are well-mixd, & set aside.
Step #2 Heat the grill, turning them once, place on the grill & grill them until they are lightly browned on both sides, brush the French bread slices on both sides with the olive oil, about 2-3 mins.
Step #3 Spread about 1 tsp of the mustard mixture onto each of the toasted bread slices; add a couple of slices of cucumber, top this with the smoked salmon & garnish with the reserved sprigs of fresh dill.
Step #4 Chef's Notes: The cucumber, mustard mixture & toasted bread can all be prepared ahead of time.
Step #5 Chill the cucumbers & the mustard mixture; & assemble the crostini just before serving.