Lay out your bread slices on a clean work surface. If you're using Dijon mustard, spread a thin layer on one side of each slice.

Layer turkey slices evenly on four bread slices. Add two slices of cheese on top of the turkey.

Sprinkle with garlic powder if using, and add a pinch of salt and pepper.

Close the sandwiches with the remaining bread slices.

Mix softened butter with a pinch of garlic powder (if using) and spread on the outside of each sandwich.

Heat a large skillet or griddle over medium heat.

Place sandwiches in the pan and cook for 3-4 minutes until golden brown.

Flip carefully and cook for another 2-3 minutes until the cheese is melted and both sides are crispy.