Slice sour dough bread into 6 thin slices. If larger pieces of bread, slice 3 pieces and cut in half.
Melt butter and mix in garlic powder.
Using a knife, spread mayo onto 3 of the 6 slices of bread.
Cut the cheese slices in half and place 1-2 pieces of each cheese onto the bread.
Top bread to create a sandwich then brush melted garlic butter onto both outer pieces of your sandwich.
Place sandwich into a hot frying pan or flat top so that it can being melting cheese.
Flip the sandwich after 2-3 minutes and repeat until both sides are crispy & cheese is completely melted.
Remove from heat, repeat until all sandwiches are completed. Serve & enjoy!