1.Mix Together Yogurt, Feta Cheese, Mint And Pepper; Set Aside. 2.Divide The Ground Meat Into 12 Equal Portions. Shape Each Portion Into A Thin Pattie, About 4-Inch Wide. Place One Tbsp. Of The Yogurt Feta Mixture Onto 6 Of The Patties, Then Top With The Remaining Meat Patties, Being Careful To Seal The Mixture In. 3.Grill Or Broil The Stuffed Burgers For About 5-8 Minutes, Turning Once. Serve Immediately On The Split Pitettes (Or Rolls) With A Slice Of Tomato And Remaining Yogurt Sauce.