Place oven rack in lower-middle position and heat to 350°.
Lightly spray bottom and sides of a loaf pan with vegetable oil spray and set aside.
Break up ground lamb and beef into a large bowl and add bread crumbs, parsley, egg, egg white, garlic, cumin, salt and pepper; using clean hands, combine the mixture well, then lightly press meat mixture together, lift it out of the bowl and place in prepared pan.
Using a small spatula, pull mixture up and away from the sides of the pan and smooth out the top.
Bake 60 minutes, or until a thermometer inserted in the center reads 150°; cool to room temperature, remove from pan and wrap in plastic wrap, then into foil; refrigerate until serving time.
Before serving, slice the chilled meatload and cook in a nonstick frying pan until crisp; serve in pita rounds (which you can warm and brown in the same pan as the meat) with tzatziki sauce**there are many excellent tzatziki sauces listed here on Zaar so I didn't add my own, do a search and choose what looks best to you.