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Broccoli Rabe Sandwich with Balsamic Onions & Red Pepper Sauce

This broccoli rabe sandwich is one of my favorite vegetarian sandwiches yet. It has enough elements to keep every bite interesting, but it's still fun to make, great for meal prep, and easy to assemble. This sandwich has a quick and slightly spicy red pepper sauce, balsamic glazed onions, charred and bitter broccoli rabe, and smoked mozzarella to bring it all together. It's a vegetable-packed, melty, cheesy sandwich, and I can't get enough.
Prep Time:15 minutes
Cook Time:30 minutes
Total Time:45 minutes
Course: Lunch, Main Course
Cuisine: American, Fusion
Keyword: baguette, broccoli rabe, mozzarella, onion, red peppers
Servings: 3 servings

Equipment

  • 1 large sauté pan
  • 1 serrated knife
  • 1 Baking sheet
  • 1 small blender

Ingredients

  • 1 medium baguette sliced into 3 pieces
  • 1/2 cup roasted red peppers drained
  • 1 & 1/2 teaspoons Calabrian chili paste
  • Kosher salt and freshly ground black pepper to taste
  • 1 medium yellow onion
  • 1 tablespoon salted butter or vegan butter alternative
  • 1 tablespoon olive oil plus more as needed
  • 1 tablespoon balsamic glaze
  • 1 pound broccoli rabe
  • 3 ounces smoked mozzarella sliced

Instructions

  • Slice each piece of the baguette in half, you should have enough for 3 big sandwiches. Set the pieces aside.
  • In a small blender add the red peppers, calabrian chili paste and a shallow 1/4 cup of water. Blend until you have a smooth sauce. Season with kosher salt and black pepper to taste.
  • Thinly slice the onion and place a large sauté pan over medium heat. Melt the butter in the pan, then add a tablespoon of olive oil. Add the onion and season with a pinch of salt. Cook, stirring occasionally, to let the onion *almost* caramelize. True caramelization takes up to 40-45 minutes, but in the interest of time, I cooked mine for about 20-25, letting the onions get soft, jammy, and lightly brown.
  • When the onions are almost done, drizzle the balsamic glaze over them. Give everything a quick mix in the pan, then transfer to a small bowl.
  • Cut the broccoli rabe in half, then into long strips, slicing through the center of the stem pieces. Add the broccoli rabe to the same pan you cooked the onions, and top them with a drizzle of olive oil and pinch of salt.
  • Shake the broccoli rabe around the pan, letting it charr in some places. Cook for about 3 minutes on each side before removing from the pan.
  • Assemble each sandwich with the red pepper sauce first, then a layer of broccoli rabe, then slices of smoked mozzarella. Broil this in an oven or toaster oven for 5 minutes, or until the cheese is melty. Add the onions to the other slice of the baguette, smash together, and eat.