Stir together the flax meal and very hot water. Set aside.
In a food processor, pulse the mushrooms until finely diced. Sauté in a large skillet on medium low heat until almost dry.
Pulse the walnuts a few times. Then add to the mushrooms, stirring occasionally, until the mixture is dry.
Meanwhile, pulse all of the vegetables in the food processer until finely diced.
Sauté the vegetables in a separate skillet on medium low heat until dry.
Pulse the beans and rice. Add to the mushroom-walnut mixture and stir to combine. Continue to sauté, breaking it up. Then turn off the heat and allow to cool slightly.
Add minced garlic and continue to sauté the vegetables until mixture is dry. Then turn off the heat and allow to cool a little.
Pulse the oats until fine.
In a large bowl, combine the oats and all of the remaining ingredients, including the vegetable mixture and the mushroom/bean/rice mixture.
Stir until combined. I found it’s easier to do this with my hands.
Form the dough into equal size balls – 4 ounces for large patties, 3 ounces for regular, and 2 ounces for sliders.
Turn on the oven or grill to 350° F. This gives the patties 15-30 minutes to rest.
Bake or grill for 20-30 minutes, until cooked firm.
Serve on hamburger buns with desired condiments and toppings.
Notes
* If you prefer, you can substitute ketchup or barbecue sauce for the tomato paste.You can use any kind of nut (including cashews or almonds), but walnuts are softer, contain a nice neutral flavor, and provide a great firm texture in this veggie burger.These veggie burgers are great on pretzel rolls, hamburger buns, or english muffins.