Cooking Instructions

Begin by peeling and slicing the onions into uniform 1/8-inch thick slices. Heat a skillet over medium-low heat, and add 2 tablespoons of unsalted butter and 1 tablespoon of olive oil.

Once the butter has melted, add the sliced onions to the skillet. Season with salt and pepper, and cook, stirring every few minutes, for about 25-30 minutes until the onions are caramelized and golden brown. If desired, sprinkle a teaspoon of sugar to enhance the sweetness.

After the onions are caramelized, deglaze the skillet with a splash of beef or vegetable broth, scraping up any bits stuck to the bottom. Allow the broth to reduce slightly, then remove the skillet from heat.

While the onions cool slightly, butter one side of each slice of bread generously. If using, spread a thin layer of Dijon mustard on the unbuttered side of the bread.

Layer slices of Gruyère cheese, a generous portion of caramelized onions, and slices of provolone cheese between two pieces of bread, buttered side out. Press gently to adhere.

Preheat a skillet to medium heat. Place the assembled sandwiches in the skillet and grill for 3-4 minutes on each side until the bread is golden brown and the cheese is melted. Adjust the heat as necessary to avoid burning.

Once cooked, remove the sandwiches from the skillet and let them sit for a minute before slicing them diagonally. Serve immediately, optionally garnished with fresh parsley or thyme.

For best results, keep an eye on the onions as they caramelize; stirring too frequently can hinder the process, while not stirring enough can lead to burning.

Feel free to customize your sandwich by adding thinly sliced roast beef or turkey for added heartiness, or try a vegetarian version with sautéed mushrooms. Leftovers can be stored in an airtight container for up to two days and reheated in a 350°F oven or in a skillet to maintain that crunchy texture. Enjoy your culinary creation!