Wet The Bread With Cold Water And Squeeze Out The Excess; Mix Well With The Chopped Meat. Add The Onion, Parsley, Mint, Egg Whites, Salt & Pepper. Shape Meatballs, Flour Lightly; Fry In Fat. To Make Sauce, Brown The Butter In A Saucepan; Add Scallions; Saute Until Golden. Add Vinegar And Water, Cook Until Only Half The Liquid Remains. Beat Egg Yolks Very Thoroughly In Bowl. In Another Bowl, Mix Cornstarch In Milk, Add This Mixture To The Egg Yolks, Then Blend In Some Liquid From The Pot, Beating All The While. Pour Egg Mixture Over Meatballs, Shaking Pot Gently Until Sauce Thickens.