Start by cooking the buckwheat groats: Add the buckwheat groats and the water to a saucepan. Heat over medium heat and bring to a boil. Reduce to a simmer and cook uncovered for 7 minutes.
Taste to check if the buckwheat is cooked, it should not be mushy or crunchy, it should be soft with some texture. Drain, discard the cooking water and set aside the cooked buckwheat.
Preheat the oven to 350°F (175°F).
Heat a tablespoon of oil in a skillet over medium heat. Once hot, add the diced onion and garlic and cook until fragrant, about 3 minutes.
Add the sliced mushrooms and cook for another 6-8 minutes. Stir in the tomato paste, soy sauce, maple syrup, spices, oregano, and onion powder. Cook for another 30 seconds and remove from heat.
Transfer the mushroom mixture to the bowl of a food processor. Add the cooked red kidney beans, parsley, almond flour, breadcrumbs, and pecans. Pulse for 5-7 seconds, or until it has a coarse texture.
Add the cooked buckwheat to the food processor and pulse for another 3-5 seconds. You don't want to process too much to keep some texture, you should still see some whole buckwheat groats.
Transfer the mixture to a large mixing bowl, add the vital wheat gluten and mix using a wooden spoon until fully incorporated. With slightly wet hands, shape the mixture into balls (I used about 1.5 tbsp for each ball) and place them on a baking sheet lined with parchment paper.
Bake the "meatballs" for 20 minutes. In the meantime, prepare the teriyaki sauce.
In a small mixing bowl, combine the soy sauce, maple syrup, lime juice, sesame oil, minced garlic, and cornstarch together.
Once the meatballs are ready, heat a tablespoon of oil in a skillet over medium heat. Add the meatballs and shallow-fry until golden brown, about 3 minutes. Remove from heat and pour in the teriyaki sauce. Stir to coat the balls with the sauce.
Serve the teriyaki meatballs immediately on a bed of rice or noodles and some greens on the side.
Meatballs will keep in the refrigerator for up to 3 days. Reheat gently in a skillet, adding more sauce if needed.