Cook Barley: Preheat the oven to 400°F (200°C). In a medium saucepan, bring 4 cups of water and 1 tablespoon of salt to a boil. Add the barley and bay leaf, then reduce the heat to medium-low. Let it simmer, uncovered, for 25–30 minutes, or until the barley is al dente. Drain well and transfer barley to a large bowl. Remove the bay leaf and let the barley cool for about 15 minutes.
Roast Mushrooms and Garlic: Toss mushrooms with tamari, 2 tablespoons olive oil, pepper, and 1/4 teaspoon salt. Spread the barley in a single, even layer on a large baking sheet. Place garlic halves on a piece of aluminum foil, drizzle with 1 teaspoon olive oil, and wrap tightly. Place foil packet next to mushrooms on the baking sheet. Roast for 40 minutes, stirring mushrooms twice during cook time, until browned and starting to dry. Let cool 10 minutes. Remove the skins from the garlic cloves and set them aside.
Prepare Burger Mixture: Pulse cooled barley in a food processor until roughly chopped (about 15 pulses). Transfer to a large bowl. Stir the carrots, beets, cumin, and smoked paprika into the barley. Pulse the roasted mushrooms in a food processor for about 10 pulses, or until finely chopped. Add chickpeas to the food processor; pulse until roughly chopped (about 10 pulses). Transfer 1 cup of chopped chickpeas to the barley mixture. Process the roasted garlic cloves and remaining chickpeas in a food processor until smooth. Add this mixture to the barley mixture. Stir in panko breadcrumbs, walnuts, and Dijon mustard until well combined. Shape mixture into 8 patties, each about 1/2-inch thick and 1/2 cup in size.
Cook Patties: Heat 2 tablespoons olive oil in a skillet over medium heat. Sear 4 patties at a time, cooking 2 minutes per side until golden and crispy. Repeat with remaining patties. Transfer seared patties to a baking sheet and bake at 400°F for 10 minutes, until tops and sides are crispy.
Assemble and Serve: Toast buns, if desired. Spread vegan mayonnaise on the bottom bun. Add lettuce, pickles, red onion, tomato, and a patty. Top with vegan cheese and cover with the top bun.
Enjoy your hearty and flavorful veggie burger! 🌱🍔