Preheat the oven to 375°F;
Drain the rinse the black beans, mash with a potato masher till mostly crushed, but leaving a little texture;
In a non-stick frying pan, sauté chopped onions avocado oil over medium high heat until golden brown and slightly caramelized, add in the carrots and shiitake mushrooms, cook till they're softened;
Season with tamari sauce, balsamic vinegar and coconut amino, stir to combine everything well, set aside to cool down;
In a large bowl, mix together mashed beans, grated beets, sautéd onions, carrots, and mushrooms, flours and all the dry spices;
Rub a little oil on your hands to prevent sticking, and hand form the mixture into patties of your preferred size;
Transfer onto a baking tray lined with parchment paper, bake for 30-35 minutes, flip half way through;
Assemble the burger with your preferred fixings or serve as a burger salad bowl, enjoy!