Cooking Instructions:

Begin by caramelizing the onions. In a skillet over medium heat, melt 1 tablespoon of butter. Add the sliced onions and a pinch of salt. Cook, stirring occasionally, for about 15-20 minutes or until the onions are golden brown and soft. If the onions start to stick, add a splash of water to help deglaze the pan. Once caramelized, remove them from the skillet and set aside.

In the same skillet, add another tablespoon of butter and allow it to melt. Place one slice of bread in the skillet, and layer half of the shredded cheese on top of the bread. Add the caramelized onions evenly over the cheese, and then top with the remaining cheese. Finally, place the second slice of bread on top to create a sandwich.

Cook the sandwich for about 3-5 minutes on medium heat, or until the bottom is golden brown and the cheese begins to melt. Use a spatula to carefully flip the sandwich over and cook for an additional 3-5 minutes on the other side until it's also golden brown and the cheese is fully melted.

Once cooked, remove the sandwich from the skillet and let it sit for a minute before slicing. This will help the cheese set a little and make it easier to cut. Serve warm and enjoy!

For extra tips, consider adding a dash of your favorite hot sauce or a sprinkle of fresh herbs like thyme or basil to the onions while they caramelize for an extra layer of flavor. Additionally, using a heavier skillet or a panini press can help achieve an evenly toasted sandwich. Don't be afraid to experiment with different cheeses or even add slices of tomato or crispy bacon for a heartier version!