You might be able to tell from the incredibly dense recipe that this is from Cook's Illustrated. It makes a ton of burgers, you could make it at the beginning of summer and freeze them individually to have for the rest of the summer. Warning, this take a couple of hours to make...
3/4 cup dried brown lentils, rinsed and picked over (if using canned, a 15 oz can will work, strain in mesh strainer with cold running water and spread them out on paper towels to dry)
2 1/2 tsps salt
3/4 bulgar wheat
2 tbls vegetable oil
2 medium onions, chopped fine (2 cups)
1 large celery rib, chopped fine ( 1/2 cup)
1 small leek, white and green parts only, chopped fine (1/2 cup)
2 medium garlic cloves, minced or pressed through garlic press (2 tsps)
1 lb cremini or white mushrooms, cleaned and sliced about 1/4 in thick (about 6 1/2 cups)
1 cup raw, unsalted cashews
1/3 mayonaise
2 cups panko
ground black pepper
1. bring 3 cups water, lentils and 1 tsp salt to boil in a medium sauce pan over high heat; reduce heat to medium low and simmer, uncovered, stirring occasionally, until lentils are just beginning to fall apart, about 25 minutes. Drain in a fine mesh strainer. Line baking sheet with triple layer paper towels and spread drained lentils over. Gently pat dry lentils with additional paper towels. Cool at room temp.
2. While lentils simmer, bring 2 cups water and 1/2 tsp salt to boil in a small saucepan. Stir bulgar wheat into boiling water and cover immediately. Let stand off heat until water is absorbed (15-20 minutes). Drain in a fine mesh strainer, use a rubber spatula to press our excess moisture. Transfer bulgar to medium bowl and set aside.
3. Heat 1 tbls oil in a 12 inch nonstick skillet over medium heat until shimmering. Add onions, celery, leek and garlic. Cook, stirring occasionally, until veggies begin to brown, about 12 minutes. Spread mushrooms on baking sheet with veggie mixture; cool to room temp - about 20 minutes.
4. Process cashew in food processor until finely chopped (about 15, 1 sec pulses). Do not wash blade or bowl. Stir into bowl with bulgar, along with cooled lentils, veggie mushroom mix and mayo. Transfer 1/2 of mixture to now empty food processor and pulse until coarsely chopped, 15-20, 1 sec pulses- mixture should be cohesive, but roughly textured.
5. Transfer processed misture to large bowl; repeat with remaining unprocessed mixture and combine into first batch. Stir in panko, 1 tsp salt, and pepper to taste. Line baking sheet with paper towels. Divide mixture into 12 portions, about 1/2 cup each, shaping into tightly packed patty, 4 inches in diameter adn 1/2 inch thick. Set patties on baking sheet, towel will absorb moisture.
Grill cook: build a medium hot grill charcoal grill or gas grill on high. Using tongs, wipe grate with towels dipped lightly in veggie oil. Grill burgers, without moving them, until well browned, 5 minutes. Flip and cook for another 5 minutes. Hooray! You've successfully made the world's most complex veggie burger. Enjoy!