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- 4 slices of sourdough bread - 1 medium onion, thinly sliced - 1 tablespoon butter - 1 teaspoon olive oil - 1 teaspoon sugar - 1/2 teaspoon salt - 1/4 teaspoon black pepper - 1 cup shredded Gruyère cheese - 1/2 cup shredded sharp cheddar cheese - 1 tablespoon fresh thyme leaves (or 1 teaspoon dried thyme) - 2 teaspoons balsamic vinegar - 1 tablespoon Dijon mustard (optional)

Gooey French Onion Grilled Cheese

Indulge in the ultimate comfort food with my Gooey French Onion Grilled Cheese recipe! This delicious twist on a classic features caramelized onions and a blend of rich cheeses for a mouthwatering experience. Perfectly toasted sourdough adds the finishing touch. Dive into each step to create this irresistible delight that will have you craving more. Click to explore the full recipe and treat yourself to cheesy goodness!
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Ingredients
  

4 slices of sourdough bread

1 medium onion, thinly sliced

1 tablespoon butter

1 teaspoon olive oil

1 teaspoon sugar

1/2 teaspoon salt

1/4 teaspoon black pepper

1 cup shredded Gruyère cheese

1/2 cup shredded sharp cheddar cheese

1 tablespoon fresh thyme leaves (or 1 teaspoon dried thyme)

2 teaspoons balsamic vinegar

1 tablespoon Dijon mustard (optional)

Instructions
 

Caramelize the Onions: In a medium skillet, heat the butter and olive oil over medium heat. Add the thinly sliced onion, sugar, salt, and pepper. Sauté for 15-20 minutes, stirring frequently, until the onions are soft and deeply caramelized. If the onions start to stick to the pan, add a splash of water to deglaze. Stir in the balsamic vinegar and fresh thyme. Cook for an additional minute, and then remove from heat.

    Prepare the Bread: While the onions are caramelizing, spread a thin layer of Dijon mustard on one side of each slice of sourdough bread (if using).

      Assemble the Sandwich: On the uncoated side of two slices of bread, layer half of the Gruyère cheese, followed by half of the cheddar cheese, then a generous amount of caramelized onions, and top with the remaining cheese. Place the other two slices of bread on top, with the mustard side facing inward.

        Grill the Sandwiches: Heat a non-stick skillet or griddle over medium-low heat. Place the sandwiches in the skillet and cook for about 4-5 minutes on each side, or until the bread is golden brown and the cheese is melty and gooey. You may want to press down lightly on the sandwiches with a spatula to encourage even browning.

          Serve: Once both sides are perfectly golden and the cheese is thoroughly melted, remove the sandwiches from the skillet and let them sit for a minute before slicing.

            - Presentation Tips: Cut the sandwiches diagonally and serve on a rustic wooden board with a small bowl of warm French onion soup for dipping, and garnish with a sprig of thyme for a touch of elegance.

              Prep Time: 10 minutes | Total Time: 30 minutes | Servings: 2