You are here: Home » Recipes » Portobello Burgers with Spinach Pesto Portobello Burgers with Spinach Pesto Recipe by Our Cookbook Collection Yield 4 servings You won't miss the meat in this juicy, flavorful mushroom-based burger PrintEmail Ingredients Spinach Pesto:2 cups baby spinach, packed1/4 cup walnut pieces, toasted1/4 cup grated pecorino Romano or Parmigiano-Reggiano cheese (a generous handful)1 clove garlic, grated or pasted A few grates of nutmeg Kosher salt and pepper1/4 to 1/3 cup EVOO (extra virgin olive oil)Portobello Caps:4 large portobello mushroom caps1/4 cup extra-virgin olive oil2 tablespoons Worcestershire sauce2 tablespoons balsamic vinegar2 tablespoons finely chopped rosemary1/2 pound fresh mozzarella or smoked fresh mozzarella, thinly sliced4 crusty rolls, split Baby spinach leaves Thinly sliced red onions Instructions Make the spinach pesto: Place the spinach in a food processor with the walnuts, cheese, garlic, and nutmeg; season with salt and pepper. Turn on the processor and stream in enough EVOO to form a thick pesto. Make the portobellos: Brush the portobello caps with a damp towel to clean them. In a large plastic food storage bag, combine the EVOO, Worcestershire sauce, balsamic vinegar, and rosemary. Add the mushroom caps and slush around to coat with seasonings. Heat a grill pan or large skillet over medium-high heat. Shake the marinade off the mushrooms and cook the caps, turning once, 10 to 12 minutes, or until well browned on both sides. Season with salt and pepper. Top the caps with the mozzarella, remove the pan from the heat, and tent loosely with aluminum foil. Let stand 1 to 2 minutes to melt the cheese. Place the mushrooms on the roll bottoms and top with pesto, a mound of baby spinach, and a few slices of red onion. Set the roll tops in place. Copyright © 2012 by Rachael Ray from THE BOOK OF BURGER published by Atria Books, a division of Simon & Schuster, Inc.