Take the frozen black beans out of the freezer, open the sealed bag (or the lid of the container) and set on the counter for 10-15 min. While thawing, it will release moisture and look 'wet' - that is OK.If using canned beans, place in a strainer for 5-7 min to remove canning liquid - do not rinse the beans; a little bit of liquid stuck to the beans is OK. For starting with dry, uncooked beans, see Recipe Notes for cooking instructions. Mince the carrots by hand or with an electric chopper.
Place in a small microwave-safe glass or ceramic bowl and microwave for 2 min on high; the volume will shrink significantly and the color will change from bright orange to a dull orange.
Once thawed, transfer the beans to a microwave-safe glass/ceramic bowl: microwave for 2-3 min on high. Mash them, just a little, with the back of a wooden spoon. Add the Mexican seasoning, mix, and microwave on 40% power for 4-5 min.
Meanwhile, chop onions. Place in a small microwave-safe glass or ceramic bowl, add butter and microwave on high for 2 min. Plastic microwave-safe bowls are not recommended for this step. The onions will become transparent and may start to brown a little in the edges.
While the onions are being sauteed, rinse and chop the cilantro. If the stems are tender, you can use them too, just chop them very finely. Add the carrots, onions salt and oatbran and gently mix. Taste a bit of the mixture and adjust salt and seasonings as per your preference. If you want it to be more spicy, add a little (upto 1/2 tsp) ground cayenne pepper
Use a 1/4 cup measure to divide into 6 portions. Gently shape each portion into a smooth ball, then flatten slightly to make a thick patty. Lightly grease your hands with oil if needed to prevent the mixture from sticking to your hands too much.
Place breadcrumbs in a small bowl, and coat each patties by gently rolling it around as needed. Only a little will stick to the patty - that's all you need.You can refrigerate or freeze them at this stage, if you wish: see Recipe Notes for storage instructions. Heat a non-stick frying pan for 2-3 min on medium. Add 2-3 drops of oil on one spot and place a patty directly on top on it. Repeat for each of the patties. Cook on medium high heat, about 2-3 min, checking periodically to see if the bottoms have browned - carefully flip one with a small turner/spatula to check, flipping back to continue browning. When the bottoms have browned, add a few drops of oil on top of each patty, then flip each one carefully. The patties are delicate and can get smashed and shapeless if not handled gently.
Add a few more drops of oil, as needed, along the edges of the patties, and cook for 2-3 min till browned. Gently press down each patty with the back of the turner, so the bottom flattens out nicely against the pan. This will allow the patties to brown evenly. You only need about 1/2 tsp oil per patties.
Serve hot off the griddle, accompanied by your favorite condiments - ketchup, sour cream, mustard, etc. Enjoy!
For storing left-over patties, see Recipe Notes.