In A Medium Bowl, Combine Cream Cheese, Mayonnaise, Shredded Cheese And Garlic Salt. Beat Until Smooth. Preheat A Large Skillet Over Medium Heat. Spread Cheese Mixture On 4 Slices Of Bread, Then Top With The Other 4 Bread Slices. Lightly Butter Both Sides Of Each Sandwich. Place Sandwiches In Skillet, And Grill Until Golden Brown On Both Sides, About 4 Minutes Per Side.