Cordon Bleu Casserole

• 4 cubed turkey (cooked)
• 650 gr cubed ham (cooked)
• 475 ml cream (light)
• 140 gr cheddar cheese (shredded)
• 120 gr onion (chopped)
• 110 gr dry bread crumbs
• 55 gr butter
• 40 gr all purpose flour
• 30 gr walnuts (chopped)
• 9 gr melted butter