1Heat oven to 375°F. Cook and drain manicotti shells as directed on package.
2In 3-quart saucepan melt butter over medium heat. Cook mushrooms, 2 tablespoons onion and garlic in butter about 3 minutes, stirring frequently, until vegetables are crisp-tender. Stir in sherry, lemon juice, lemon pepper and salt. Cook over medium-high heat about 4 minutes, stirring occasionally, until almost all liquid has evaporated. Stir in whipping cream. Heat to boiling, stirring constantly. Boil over medium-high heat about 1 minute, stirring frequently, until slightly thickened.
3In small bowl, mix cream cheese, feta cheese, 2 tablespoons onion and the Worcestershire sauce with fork until well blended. Stir in ham and chives. Fill each shell with about 3 tablespoons of the cheese mixture, using small spoon.
4Pour half of sauce unto ungreased 8-inch square (2-quart) glass baking dish. Arrange filled shells in dish. Spoon remaining sauce over shells. Cover and bake about 20 minutes or until hot and bubbly.