1. Prepare the Patty Base:

• Heat the olive oil in a large skillet over medium-high heat. Add the finely chopped mushrooms and onion. Cook, stirring occasionally, for 10-12 minutes, until the vegetables have released all their moisture and are deeply browned and caramelized.

• Add the minced garlic and cook for one more minute until fragrant.

• Remove the mixture from the heat and set it aside to cool slightly. This step is crucial for developing flavor and preventing a soggy patty.

2. Form the Veggie Patties:

• While the mushroom mixture cools, place the toasted walnuts in a food processor and pulse until they are the texture of coarse crumbs. Transfer them to a large mixing bowl.

• Pat the rinsed black beans very dry with a paper towel. Add half of the beans to the food processor and pulse a few times until roughly chopped (you want some texture, not a paste). Add these to the bowl with the walnuts.

• Add the remaining whole black beans to the bowl.

• Add the cooled mushroom and onion mixture, Panko breadcrumbs, egg (or flax egg), nutritional yeast, soy sauce, smoked paprika, salt, and pepper to the bowl.

• Using your hands or a sturdy spoon, mix everything together until just combined. Be careful not to overmix. The mixture should be thick and hold its shape.

• Divide the mixture into 4 or 5 equal portions and form them into patties about ¾-inch thick.

3. Chill the Patties (Important!):

• Place the formed patties on a parchment-lined baking sheet or plate. Cover and refrigerate for at least 30 minutes, or up to 4 hours. This chilling step is essential for the patties to firm up and hold their shape during cooking.

4. Cook the Mushroom Topping:

• While the patties chill, wipe out the skillet and melt the butter over medium heat.

• Add the sliced mushrooms and cook, stirring occasionally, until they are browned and tender (about 5-7 minutes).

• Add the minced garlic, a pinch of salt, and pepper, and cook for another minute. Remove from the skillet and set aside.

5. Cook the Veggie Burgers:

• Heat a thin layer of oil in the same skillet over medium-high heat.

• Carefully place the chilled patties in the hot skillet. Cook for 4-5 minutes per side, until a deep brown crust has formed and the patties are heated through. Be gentle when flipping them.

• During the last minute of cooking, top each patty with a slice of Swiss cheese, cover the pan, and let it melt completely.

6. Assemble Your Masterpiece:

• Toast your burger buns on the skillet or under a broiler until golden.

• Spread your desired sauce (garlic aioli or dijonnaise) on the top and bottom buns.

• Place a piece of lettuce on the bottom bun (this helps prevent it from getting soggy).

• Add the cheesy veggie patty, top with a generous pile of the sautéed mushrooms, and place the top bun on.

• Serve immediately and enjoy!