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Caramelized Onion Grilled Cheese Sandwiches With Miso Butter

Created by ForeverMama on May 10, 2022

1 tablespoon extra-virgin olive oil
1 large yellow onion (1 pound), thinly sliced
1/8 teaspoon kosher salt
1 tablespoon rice vinegar, preferably unseasoned
3 tablespoons unsalted butter, at room temperature (may substitute vegan butter, such as Earth Balance), divided

2 teaspoons white or dark miso paste
1 tablespoon whole-grain mustard
4 slices good-quality sandwich bread
4 ounces grated Gruyere cheese (1 cup; may substitute vegan shredded cheese, such as Violife or Daiya)
Cornichons (a.k.a. gherkins), for serving (optional)

Step 1: In a large skillet over medium-high heat, heat the oil until shimmering. Add the onion and salt and cook, stirring often, until the onions start to soften and brown, 5 to 6 minutes. Reduce the heat to medium-low and cook, stirring occasionally, until the onions are deeply browned and sticky, 30 to 45 minutes. Stir in the vinegar. Transfer the onions to a small bowl.
Step 2: In a small bowl, mix 1 tablespoon butter with the miso paste and mustard. Spread one side of each bread slice with the miso butter. Spread the other sides with the remaining 2 tablespoons butter.
Step 3: Return the skillet to medium-low heat. Place two of the bread slices, plain-buttered-side down, in the skillet. Divide the cheese and onions evenly between them and top with the other bread slices, plain-buttered-side up. (You want the miso butter on the inside of the sandwiches.) Cook until the bread is golden brown, 5 to 7 minutes. (Resist the urge to press the sandwich with a spatula.) Flip the sandwiches over and cook on the other side until the bread is golden brown and the cheese is melted, 5 to 7 minutes. Transfer to plates and serve with cornichons, if desired.