• Place walnuts in a bowl and cover in boiling water; set aside for thirty minutes.
• In the meantime, process mushroom and onions in a food processor until chopped; remove and add to a large bowl.
• Add the cooked brown rice and rolled oats to the food processor until chopped and ground; add to bowl with mushrooms.
• Lastly, add the soaked walnuts into the food processor until finely ground, and add to same bowl.
• Add beets, soy sauce, tomato paste, garlic, flaxseed and flour to the mushrooms, onions, oats, and walnut mixture and mix with hands until completely combined.
• Chill burger for one hour.
• Shape mixture into four equal-size patties.
• Oven Cooking
• Heat oven to 176 °C (350°F) and cook the burgers for 40 minutes in total; flipping halfway through.

Pan Cooking

• Heat one tablespoon of olive oil over medium heat; cook burgers for seven to ten minutes on each side or until slightly browned and cooked through.
• Serve on beetroot bun with your favourite burger toppings!