We topped these burgers with smoked Cheddar cheese, but you can use another type of cheese, or omit it entirely. To clean the mushroom caps, wipe them with a damp paper towel; do not rinse or soak them because they will remain soggy even after cooking.
Recipe information
Yield
makes 4
Ingredients
Preparation
Step 1
Heat a grill or grill pan over medium heat. Make the bean puree: In a food processor, combine one-quarter of the garlic (about 1/2 teaspoon), 1 tablespoon thyme, the cannellini beans, and 1 teaspoon oil; process to form a smooth and spreadable paste. If the mixture is too thick, add 1 teaspoon water. Season with pepper, and pulse to combine. Set aside.
Step 2
Combine the remaining garlic, tablespoon thyme, and oil on a plate or in a baking pan. Place the mushroom caps in the garlic mixture, and turn to coat. Season with pepper; drizzle with vinegar.
Step 3
Place the onion slices on a plate, and lightly coat each side with cooking spray. Grill the onions until lightly charred on the first side, about 3 minutes. Flip the onions, and continue grilling until tender and charred on the other side, about 3 minutes more. Transfer to a clean plate; keep warm.
Step 4
Place the mushrooms on the grill, stem side up, working in batches if necessary. Grill until browned on the first side and juices have begun to collect in the centers, about 5 minutes. Flip the mushrooms, and continue cooking until the stem side of each cap is browned and center is tender, about 4 minutes more.
Step 5
Split the hamburger buns in half, and place cut side down on the grill; cook until warm and toasted. Transfer to a work surface. Spread 1/4 cup bean puree on the bottom half of each bun, and top with 2 grilled mushroom caps. Layer each with sliced cheese, grilled onions, and a small handful of arugula. Top each with matching roll halves, and serve.
