In a small bowl, mix the softened butter, garlic powder, and parmesan cheese together.
3 tbsp butter, 3 tbsp parmesan cheese, 1/2 teaspoon garlic powder
Spread the butter mixture on the outside of the sourdough bread slices.
4 sliced sourdough bread
Place 1 & 1/2 slices of mozzarella and 1 & 1/2 slices of white cheddar on the non buttered side. Top the sandwich with the remaining piece of toast, keeping the buttered side outside.
3 slice white cheddar cheese, 3 slices mozzarella cheese
Heat a large pan or skillet on medium-low heat, place the sandwiches on there and toast each side for 1-2 minutes or until the outside is toasty and the cheese is melted. Want the cheese to melt faster? Cover with a lid.
Remove the grilled cheeses from the pan, slice in half, and enjoy!