Step 1

In a medium bowl with an electric mixer, beat mayonnaise and cream cheese until light and fluffy. Stir in Cheddar cheese, mozzarella cheese, and garlic powder; mix well.

Step 2

Spread each of five bread slices evenly with cheese mixture. Top with remaining bread slices. Spread butter on both sides of the sandwiches.

Step 3

In a skillet over medium heat, cook in batches until golden on both sides and the cheese is melted.