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French Onion Grilled Cheese Sandwich Recipe
Ash Tyrrell

French Onion Grilled Cheese Sandwich Recipe

I still remember the first time I made this French onion grilled cheese sandwich at home, and honestly, I didn’t expect it to taste this close to a fancy restaurant dish. I was craving something warm, cheesy, and deeply savory, and this recipe delivered all of that in every bite. The slow-cooked caramelized onions bring a rich sweetness that pairs perfectly with the melted cheese
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Total Time 55 minutes
Ingredients Method Notes

Ingredients
  

  • 2 large yellow onions thinly sliced
  • 2 tablespoons unsalted butter
  • 1 tablespoon olive oil
  • 1/2 teaspoon salt
  • 1 teaspoon sugar optional
  • 1 tablespoon balsamic vinegar or sherry vinegar
  • 4 slices sourdough bread
  • 1 cup Gruyère cheese shredded
  • 1/2 cup white cheddar cheese shredded
  • 2 tablespoons mayonnaise or softened butter for grilling bread
  • 1/2 teaspoon fresh thyme optional

Method
 

  1. I start by melting butter and olive oil in a skillet over medium-low heat. Then I add thinly sliced onions with salt and stir gently. I cook them slowly until they turn golden brown and sweet.
  2. Once onions soften, I let them cook for about 30–40 minutes. I stir occasionally so they don’t stick or burn. Then I add balsamic vinegar and thyme for extra depth.
  3. I spread butter or mayonnaise on one side of each bread slice. Then I layer Gruyère and cheddar cheese generously. I add a spoonful of caramelized onions inside.
  4. I place the sandwich on a hot skillet, butter side down. I press lightly and cook until golden and crispy. Then I flip and cook the other side until cheese melts.
  5. I remove it from the pan when both sides are crisp. I let it rest for a minute so cheese sets slightly. Then I slice and enjoy the melty, savory goodness.

Notes

  • I always cook onions on low heat; rushing ruins the sweetness.
  • I grate cheese fresh because it melts much smoother than pre-shredded.
  • I sometimes add a pinch of sugar, but I taste the onions first.
  • I use thick sourdough so the sandwich doesn’t get soggy.
  • I press the sandwich slightly while cooking for even crispiness.