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French Onion & Roast Beef Grilled Cheese Sandwich


Grilled cheese sandwiches are just fine with cheese. But when the cheese is Gruyère, and you add roast beef and caramelized onions, it's over the top.

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  • 1 tablespoon olive oil
  • 1 small onion, sliced
  • 1 teaspoon thyme leaves
  • Kosher salt
  • Pepper
  • 4 slices (1/2-inch-thick) rye bread
  • 1 tablespoon unsalted butter or olive oil, melted
  • 1 tablespoon whole-grain mustard
  • 2 ounces Gruyère cheese, grated
  • 2 slices roast beef



Step 1

Heat olive oil in a medium skillet over medium heat. Add onion, season with 1/4 teaspoon each salt and pepper, and cook, covered, stirring occasionally, about 5 - 7 minutes. Reduce the heat to medium-low, stir in thyme leaves and cook, uncovered, stirring occasionally, until the onions are golden brown, (add 1 tablespoon water to the skillet if the onions start sticking).

Brush one side of each slice of bread with butter or oil. Form sandwiches with the bread, whole-grain mustard, Gruyère cheese, roast beef, and the onion mixture. Cook the sandwiches, covered, until the bread is golden brown and crisp and the cheese has melted, 4 to 5 minutes per side.

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