Heat the oil in a large saucepan over medium heat. Once hot, add the onion and garlic. Cook for 3-5 minutes, stirring regularly until onions are soft and start to caramelize.
Add the chopped celery, carrot, and red bell pepper. Cook for another 5 minutes.
Next, add the buckwheat groats, water, diced tomatoes, cumin, chili powder, smoked paprika, oregano, salt, and maple syrup. Bring to a boil and let simmer for about 20 minutes. Check regularly to make sure there is still enough water. After 20 minutes, taste it, the buckwheat groats should be cooked, soft but not mushy.
Finally, stir in the red kidney beans and nutritional yeast. Cook for another 3-5 minutes. Taste and adjust seasonings if needed, adding more chili powder for a spicier chili, or more maple syrup for a sweeter one.
Serve hot topped with avocado slices, coconut cream, and a drizzle of lime juice.
This buckwheat chili will keep for up to 5 days in the refrigerator or up to 2 months in the freezer. For a more soupy chili, increase the water to 2 and 1/2 cups.