While cooking, saute onions and mushrooms. Roll out pastry sheet. Rub margarine in the inside of pastry sheet. Combine spinach, onions and mushrooms. Add salt and pepper to taste.
Sprinkle bread crumbs over pastry sheet.
Roll up jellyroll-sstyle. Brush egg on top. Bake at 425 degrees F for 20 to 30 minutes, until golden brown on top.