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Caramelized Onion and Spinach Grilled Cheese

A recipe for Caramelized Onion and Spinach Grilled Cheese! This sandwich is packed with caramelized onions, sautéed spinach, and melted cheese for a delicious and comforting lunch.

Prep Time
10 mins
Cook Time
10 mins
Total Time
50 mins
Servings: 4 Sandwiches
Course: Main Course
Cuisine: International

Ingredients

  • 2 tablespoons (28 grams) unsalted butter plus more for spreading over the bread
  • 1 tablespoon (15 milliliters) olive oil
  • 2 medium onions peeled and thinly sliced
  • 2 cloves garlic peeled and minced
  • 1 tablespoon (15 milliliters) balsamic vinegar
  • Salt and freshly ground black pepper to taste
  • 3 ounces (85 grams) baby spinach leaves
  • 8 slices sourdough or rustic bread
  • 1/4 cup (60 grams) Dijon mustard
  • 8 slices Swiss, Cheddar, Fontina, or Mozzarella cheese or 16 slices if small
  • 1/4 cup (60 grams) mayonnaise

Instructions

    Cup of Yum
  1. In a large pan, place the butter and olive oil over medium low heat.
  2. Once the butter is melted, add the onions and cook, stirring occasionally, until deeply golden and caramelized. Adjust heat between medium and low as needed to caramelize the onions without burning.
  3. Add the garlic and cook just until fragrant, 30 seconds to 1 minute.
  4. Stir in the balsamic vinegar and season with a large pinch of salt and pepper.
  5. Stir in the baby spinach and continue to cook until the leaves are wilted and any released moisture evaporates.
  6. Remove from heat and set aside to cool slightly.
  7. Place two slices of bread on a work surface.
  8. Brush the outside of each slice of bread with a thin layer of butter.
  9. Place the slices butter-side down on the work surface.
  10. On the inside of one slice of bread, spread a thin layer of mustard.
  11. Cover the mustard with a slice of cheese (or two if the slices are small).
  12. Cover the slice of cheese with a thin layer of the caramelized onion spinach mixture.
  13. Cover with another slice (or two) of cheese.
  14. Spread a thin layer of mayonnaise on the inside of the other slice of bread.
  15. Place the slice of bread, mayonnaise-side down, over the cheese to complete the sandwich.
  16. Repeat with the remaining slices of bread and ingredients to make four sandwiches in all.
  17. Place a skillet over medium-low heat.
  18. Gently transfer the assembled sandwich to the hot skillet. Cook, adjusting the heat between medium-low and low as needed, until the bread is golden and the cheese has melted, about 2 minutes per side.
  19. Repeat with the remaining sandwiches.
  20. Serve the Caramelized Onion and Spinach Grilled Cheese while still hot.