GRILLED MUSHROOM BURGER WITH WHITE-BEAN PUREE

Steps:

• Heat a grill or grill pan over medium heat. Make bean puree: In a food processor, combine one-quarter of garlic (about 1/2 teaspoon), 1 tablespoon thyme, the cannellini beans, and 1 teaspoon oil; process to form a smooth and spreadable paste. If mixture is too thick, add 1 teaspoon water. Season with pepper, and pulse to combine. Set aside.
• 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.
• Place 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 onions to a clean plate; keep warm.
• Place 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 mushrooms, and continue cooking until stem side of each cap is browned and center is tender, about 4 minutes more.
• Split 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 two grilled mushroom caps. Layer each with sliced cheese, grilled onions, and a small handful of arugula. Top each with matching roll halves, and serve.