Sauté the Mushrooms
Heat a pan over medium-high and add oil. Cook the mushrooms until all liquid evaporates—about 8–10 minutes. You want the pan almost dry and the mushrooms lightly browned.
Add the Aromatics
Add onions and garlic. Cook 3–4 more minutes until fragrant.
Mix the Patty Base
Combine the mushroom mixture with panko, egg, soy sauce, paprika, salt, pepper, thyme, and Parmesan if using. Taste and adjust seasoning.
Form and Chill the Patties
Shape into 4 patties and refrigerate at least 20 minutes. This helps them firm up.
Cook
Pan-fry in a little oil until crisp and browned on both sides, about 4–5 minutes per side. They can also be baked or grilled.
Assemble and Enjoy
Top with your favorite burger fixings. The earthy flavor of mushrooms pairs beautifully with cheddar, gouda, Swiss, caramelized onions, or a tangy aioli.