Grilled cheddar cheese sandwiches with tart green apples, grainy mustard, and smoky bacon on sourdough bread. Inspired by Apple, Cheddar, and Pancetta Paninis in Homemade with Love by Jennifer Perillo.
Heat a large skillet over medium heat.
Butter one side of each slice of the sourdough bread. If using mustard, spread mustard on the interior side of one of the buttered slices of bread.
Place a cheese slice on the mustard, followed by apple slices and bacon. Add another cheese slice on top of that, and close the sandwich with the other piece of buttered bread.
Grill the sandwich until crisp and browned on each side and until the cheese is melted (if your cheese is not melting, covering the sandwich with a lid can help, but turn down the heat so that the bread doesn't over-brown). Remove the sandwich from the pan, slice on the bias, and serve promptly.