Asparagus trimmed and cut in half on diagonal. Boil until barely tender-crisp, 2 minutes; drain and rinse in cold water.

Saute leek, white part only thinly sliced, in butter in a large frying pan over medium heat until soft, 5 minutes. Add thyme, 1/2 tsp salt, 1/4 tsp pepper and the morels; cook, stirring occasionally, until morels are tender, 5 minutes. Stir in sherry and reduce by half.
Set vegetables aside.

Grill salmon until barely cooked through, about 10 minutes. Add cream and asparagus to mushrooms and bring to a boil over high heat, stirring; boil longer to thicken sauce. Spoon half the vegetable sauce over the fish and the rest on the side.

Serve immediately.