These veggie burgers are hearty enough for carnivores.
1. Make the Burgers: Preheat oven to 375 degrees F. In 3-quart, shallow baking dish, toss mushrooms with walnuts, garlic, 1 tablespoon oil, 3⁄4 teaspoon salt, and 1⁄4 teaspoon pepper; spread in even layer. Bake 20 minutes or until mushrooms are tender. Set aside to cool. Turn oven off.
2. In food processor, pulse mushroom mixture, red onion, green onions, and vinegar until mostly smooth, scraping side of bowl if necessary. Transfer mixture to a large bowl and stir in quinoa and cornstarch until well-blended. Cover bowl with plastic wrap and refrigerate 2 hours.
3. Preheat oven to 375 degrees F. Line baking sheet with foil. Form mixture into 5 patties (about 1/2" thick and 3" wide). In a 12" nonstick skillet, heat remaining 1 tablespoon oil on medium. In 2 batches, cook patties 5 minutes or until well-browned, turning over once. Transfer seared patties to prepared baking sheet. Bake 10 minutes or until hot in centers.
4. Make the Rosemary Mayo: Meanwhile, combine mayonnaise, rosemary, lemon juice, and a pinch of salt. Keeps up to 5 days, refrigerated.
5. Serve burgers on buns with Rosemary Mayo, garnished with sprouts, lettuce, and tomato.
Nutritional Information (per serving): Calories 495; Protein 9g; Carbohydrate 49g; Total Fat 31g; Saturated Fat 4g; Dietary Fiber 7g; Sodium 700mg