Slice bread into 6 half-inch pieces.
Melt butter and olive oil in pan and coat each side of bread.
Toast 1 side of 4 pieces and both sides of 2 pieces of bread till dark brown but not burnt.
Use the garlic to rub all over bread, using the crustiness of the bread to lightly grate the garlic.
Mix cheeses and evenly spread cheese on one piece of bread. Lightly sprinkle with salt, top with another piece of bread. Add cheese and salt again and top off with another piece of bread. Toast until dark golden brown, and cheese is melted.
If needed to help melt cheese, put 2 teaspoons of water in the pan and cover to let steam. Don't worry this won't make grilled cheese soggy, it'll just help melt the cheese.