Use 2 Tablespoons Of The Butter To Spread Over One Side Of Each Slice Of Bread. On Three Of The Slices, Spread A Layer Of Dijon Mustard Over The Butter, And Top Each With 4 Slices Of Ham. On The Other Three, Spread Mayonnaise, And Top Each One With 2 Slices Of Swiss Cheese. Press Ham And Cheese Sides Of Sandwiches Together. In A Flat Bottomed Dish, Whisk Together The Flour, Baking Powder, Salt, Eggs, And Water Until Blended. Set Aside. Heat Remaining Butter And Vegetable Oil In A Large Skillet Over Medium Heat. Dip Both Sides Of Each Sandwich In The Egg Mixture, And Fry In The Oil And Butter Until Browned, Flipping To Brown On Each Side.