Steak And Mushroom Pie

• 1 onion (sliced)
• 1 ceramic pie bird (optional)
• 1 egg for glazing (white)
• 700 gr sirloin steak (lean)
• 120 ml beef broth
• 80 gr mushrooms (fresh sliced)
• 40 gr all purpose flour
• 3 gr salt
• 1 gr black pepper (freshly ground)