Chicken Florentine in Puff Pastry

4 chicken breasts, skinned and boned
Salt and freshly ground pepper
2 Tablespoons butter
1 (10-ounce) package frozen chopped spinach
1 cup fresh diced mushrooms
1 small onion, finely chopped
½ can cream of mushroom soup, undiluted
2 Tablespoons Madeira
¼ teaspoon salt
¼ teaspoon freshly ground pepper
1 sheet puff pastry, thawed
½ cup shredded Swiss cheese
¼ cup freshly grated Parmesan cheese
1 egg
1 Tablespoon water

Chicken: Trim all fat from chicken breasts. Wash and pat dry with paper towel. Sprinkle both sides with salt and pepper. In a skillet, melt 2 Tablespoons butter. Add chicken and sauté 5 to 8 minutes on each side, or until cooked all the way through. Remove from pan and drain on paper towels.

Spinach Mixture : Squeeze moisture from mushrooms by hand. Place in paper towel and squeeze any remaining moisture. Repeat procedure with spinach. Add mushrooms and onions to the same skillet that was used to cook the chicken; cook over medium heat 4 to 5 minutes. Add Madeira and cook 1 to 2 minutes, or until moisture evaporates. Remove from heat and add spinach, cream of mushroom soup, salt and freshly ground pepper; mix well. Set aside.

Assembly: Preheat oven to 375º F. Place puff pastry sheet on a floured surface. With floured rolling pin, roll to approximately 14 inches by 14 inches. Cut into 4 squares, 7 inches by 7 inches. Place 2 tablespoons Swiss cheese in the center of each puff pastry square. Top with 1/3 to ½ cup spinach mixture. Place cooked chicken breast on spinach mixture. Bring the shorter ends of the puff pastry up over the chicken; then bring the longer ends over the chicken to completely cover. Press the seams together. Place, seam side down in a baking dish. (Note: May be made ahead of time up to this point and refrigerated or frozen.) Make an egg wash by beating together an egg and 1 Tablespoon water. Brush the top with egg wash and sprinkle with Parmesan cheese. Bake at 375º F for 20 to 25 minutes or until done. Yield: 4 servings.