In medium skillet over medium-high heat, heat margarine. Season chicken with
salt and pepper if desired. Add chicken and cook until browned. Remove chicken
from skillet. Cover and refrigerate at least 15 minutes. Thaw pastry sheet at
room temperature 30 minutes. Preheat oven to 400 F. Mix egg and water and set
aside. Unfold pastry on lightly floured surface. Roll into 14-inch square and
cut into 4 (7-inch) squares. Spread 1 teaspoon mustard on each square. Top
with 1 slice ham, 1 slice cheese and 1 chicken breast half. Brush edges of
squares with egg mixture. Fold corners to center on top of chicken and seal
edges. Place seam-side down on shallow-sided baking sheet. Brush with egg
mixture. Bake 25 minutes or until golden.
