Heat Oil In A Deep-Fryer To 365 Degrees F (180 Degrees C). Spread One Teaspoon Of Mayonnaise Onto Each Slice Of Bread. Place 2 Pieces Of Cheese Onto One Slice Of Bread, Then Top With The Other Side Of Bread. The Mayonnaise Should Be On The Inside. In A Medium Bowl, Whisk Together The Eggs And Milk. Place The Bread Crumbs Into Another Dish. Dip Each Sandwich Into The Egg Mixture, Then Coat With Bread Crumbs. One At A Time, Immerse The Sandwiches In The Preheated Oil. Fry Until The Cheese Is Melted, And The Crust Is Golden Brown, 3 To 4 Minutes. Repeat With The Other Sandwich. Place On Paper Towel To Absorb Excess Oil Before Serving.