In A Bowl, Beat Eggs, Milk, Sugar, Vanilla And Salt. Pour Half Into An Ungreased 13-In. X 9-In. X 2-In. Baking Dish. Arrange Six Slices Of Bread In A Single Layer Over Egg Mixture. Place One Piece Of Chocolate In The Center Of Each Piece Of Bread. Top With Remaining Bread; Pour Remaining Egg Mixture Over All. Let Stand For 5 Minutes. In A Large Nonstick Skillet, Melt Butter Over Medium Heat. Fry Sandwiches Until Golden Brown On Both Sides. Dust With Confectioners' Sugar. Cut Sandwiches Diagonally; Serve Warm.