01 -
Lay your bread slices on a clean surface. Lightly coat the top of each slice with a thin smear of mayo. Turn one slice over and add a light layer of Dijon mustard to the other side. Pile the shredded cheddar and Gruyère (or raclette) on top of the mustard. Top with the second bread slice, making sure the mayo side faces outward.
02 -
Warm a nonstick or cast-iron pan over medium-low heat. Add enough butter to lightly coat the bottom of the pan and let it melt. Place your assembled sandwich in the pan, cover it with a lid, and let it cook for about 2 to 3 minutes until the bottom turns golden and crispy. Carefully flip the sandwich, cover again, and cook for another 1 to 3 minutes until the second side is beautifully browned and the cheese has melted into gooey perfection. If the bread starts browning too quickly before the cheese melts, just lower the heat a bit.
03 -
Cut the grilled cheese in half and enjoy it while it's hot and the cheese is still stretchy.