1-First, take your 2 slices of sourdough bread and spread mayonnaise thinly on the outside of both slices. This step helps create that crispy exterior we all love.

2-On the inside of one slice, spread Dijon mustard evenly to add a bit of zing.

3-Add 28 to 56 grams (1 to 2 ounces) of grated sharp cheddar cheese and 28 to 56 grams (1 to 2 ounces) of grated Gruyère or raclette cheese on top of the mustard for the perfect melt.

4-Close the sandwich with the other slice, making sure the mayonnaise side is out.

5-Heat a nonstick or cast-iron skillet over medium-low heat and coat it with butter to prevent sticking.

6-Place the sandwich in the pan, cover it, and cook for 2 to 3 minutes until the bottom is golden and crisp. If the bread browns too quickly, adjust the heat.

7-Flip the sandwich, cover again, and cook for another 1 to 3 minutes until the other side is browned and the cheese has melted perfectly.

8-Once done, remove from the heat and let it rest for a moment before serving. The whole process takes about 5 minutes to prepare and another 5 minutes to cook, totaling just 10 minutes.