Preheat the oven to 350 degrees F (180 degrees Celsius) and line a large baking sheet with parchment paper.
Add the oats to the food processor and process until coarse flour.
Cut the mushrooms and onion. Mince the garlic cloves.
Rinse and drain kidney beans.
Toast the walnuts in a pan without oil until fragrant and golden.
In another pan, heat some oil and sauté diced onions for 3 minutes. Add the minced garlic and sliced mushrooms cook for 2-3 minutes more.
Add the sautéd onion, mushrooms, and garlic along with toasted walnuts and kidney beans to a food processor and pulse until coarse.
Stir in ground oats (or bread crumbs), the flax egg, tamari sauce, tomato paste and the seasonings.
Combine well and shape into balls.
Place each ball on the prepared baking sheet an inch or two apart.
Bake for about 25-30 minutes until golden on both sides. (Gently flip the balls halfway through.)