Preheat oven to 350 degrees. Using a sharp knife, cut open each breast half, horizontally through side, being careful not to split completely. Pound lightly until flat, doubled in size and of even thickness. Season with salt and pepper.
Lay spinach leaves over surface of each chicken breast. Mix cheese with walnuts, form into 2 small logs and place one on each breast. Roll up chicken into a log shape with cheese mixture in center. Roll out enough puff pastry to envelop chicken. On a baking sheet place chicken on pastry and roll up. With a sharp knife slit top decoratively; brush with egg wash. Bake 30 minutes, until golden brown. Serve with warmed chicken stock, garnished with parsley.
Yield: 2 servings