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Onion Grilled Cheese Sandwich

This Onion Grilled Cheese Sandwich combines the rich, caramelized flavor of onions with the melt-in-your-mouth goodness of Gruyere cheese, all sandwiched between crispy, golden-brown bread. A deliciously savory treat perfect for lunch or a quick snack. The optional use of whole grain mustard adds a tangy kick that enhances the overall flavor.
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Prep Time 10 minutes
Cook Time 30 minutes
Total Time 40 minutes
Servings: 2 servings
Course: Main Course
Cuisine: American
Calories: 680
Ingredients Method Notes

Ingredients
  

Onion Grilled Cheese Sandwich Ingredients
  • 1 large red, sweet, or yellow onion thinly sliced about 1/8 inch thick
  • 1-2 tablespoons olive oil
  • generous pinch salt
  • pinch fresh cracked pepper
  • 1 tsp fresh thyme optional
  • 1/4 cup beef stock optional, or sub a splash of balsamic vinegar
  • 4 slices hearty bread or French bread
  • 1 tablespoon butter or sub olive oil
  • 1 tablespoon olive oil
  • 1 cup grated or sliced Gruyere cheese or meltable vegan cheese
  • whole grain mustard optional

Method
 

Instructions
  1. In a large heavy-bottom skillet or cast iron pan, heat olive oil over medium heat. Add the onion and sauté for 5 minutes, stirring to coat.
  2. Reduce heat to medium-low. Stir occasionally and continue sautéing for 20 minutes. The onions will sweat out their moisture and caramelize into a deep golden brown.
  3. Add a generous pinch of salt and a splash of stock (optional). Let the liquid cook off and remove the onions from the pan.
  4. Wipe the pan with a paper towel and preheat the oven to 350°F.
  5. Spread whole grain mustard (optional) on two slices of bread. Layer the shredded Gruyere cheese, then top with caramelized onions. Sprinkle with fresh thyme leaves (optional) and add the rest of the cheese.
  6. Place the other slices of bread on top to form sandwiches and gently press together.
  7. In the same pan, heat butter and olive oil over medium-low heat. Place the sandwiches in the pan and toast, carefully flipping them when golden brown and cheese begins to melt.
  8. Place the sandwiches in the preheated oven to fully melt the cheese, preventing the bread from getting too dark.
  9. Cut the sandwiches in half and enjoy.

Notes

  • For a vegan version, use meltable vegan cheese and olive oil instead of butter.
  • The stock can be skipped or substituted with balsamic vinegar for a slightly tangier flavor.