Cook the asparagus in boiling salted
water for 3-4 mins until just tender.
Drain and refresh in cold water to stop
them cooking further, then pat dry.
Cut the asparagus tips off the stalks,
so they are about 2cm long, and set
aside. Slice the stalks into small pieces.
Flake the trout into small pieces
and put in a bowl. Add the chopped
asparagus stalks, horseradish, crème
fraîche, dill and lemon juice, and
season. Chill until ready to use.
Divide between 10 vol-au-vent cases
and sit an asparagus tip and sprig of
dill on top of each.