In large nonstick skillet, combine olive oil and shallots; cook, covered, over medium heat until shallots are translucent.
Add mushrooms; continue cooking, covered, until mushrooms are soft.
Stir in soy sauce, sherry and water; simmer 1 minute.
Remove from heat; season with pepper.
Transfer mixture to medium bowl; cover to keep warm.
Coat same skillet lightly with oil.
Cook trout, flesh side down, over high heat 2 minutes.
Gently turn trout; cook 2 minutes more or until trout flakes with fork.