Heat the olive oil in a medium skillet over medium heat. Cook the shallot until soft, approximately 1 minute.

Add the mushrooms and a generous pinch of salt to the skillet. Cook until the mushrooms are soft and browned, adjusting the heat as necessary, for about 6 to 9 minutes.

Stir in the tamari, vinegar, and mirin. Reduce the heat and add the garlic, smoked paprika, and sriracha. Remove the skillet from the heat and let it cool slightly.

In a food processor, combine the sautéed mushrooms, walnuts, flaxseed, brown rice, and ½ cup of the panko. Pulse until the mixture is just combined. It should hold together when pinched but still have some texture.

Transfer the mixture to a large bowl and fold in the remaining panko.

Shape the mixture into 8 patties and place them on a large plate. Chill in the refrigerator for 1 hour.

If grilling the patties, preheat a grill to medium-high heat. Brush the patties with olive oil and spray the grill with cooking spray. Place the patties on the grill and lightly press them down with a spatula. Grill for 7 minutes on the first side, then flip and grill for another 6 to 7 minutes on the second side, or until well-charred and cooked through.

Alternatively, cook the