Thaw salmon, if frozen. Discard skin and bones. Melt margarine or butter in a large saucepan over medium heat. Add mushrooms and leeks or green onion; cook 1 or 2 minutes until tender. Stir in chicken broth, fresh dill or dried dillweed, and pepper. Bring mixture to boiling.
Combine half-and-half or light cream and cornstarch; stir into mushroom mixture. Cook and stir over medium heat until thickened and bubbly. Add salmon and simmer, covered, about 4 minutes or until fish flakes easily when tested with a fork. Gently stir in the dry sherry.