Polish Reuben Casserole

• 32 sauerkraut
• 600 ml condensed cream of mushroom
• 400 gr polish sausage
• 325 ml milk
• 250 gr swiss cheese (shredded)
• 95 gr wheat bread crumbs (whole)
• 60 gr onion (chopped)
• 55 gr width (uncooked)
• 28 gr butter
• 16 ml prepared mustard