In a small bowl, beat the cream cheese, 2 tablespoons butter, chives and lemon-pepper until blended. Stir in chicken and mushrooms.
Place a rounded teaspoonful in the center of a wonton wrapper. (Keep remaining wrappers covered with a damp paper towel until ready to use.) Fold bottom corner over filling; fold sides toward center. Moisten remaining corner with water; roll up tightly to seal.
Melt remaining butter; brush over wontons. Coat with croutons. Place on a baking sheet; freeze. Transfer to a large freezer bag; seal and freeze for up to 3 months.
To use frozen wontons: Place wontons on greased baking sheets. Bake at 425° for 10 minutes. Turn; bake 5-10 minutes longer or until lightly browned. Serve warm with sweet-and-sour sauce if desired.