Mash beans but don't puree so as to have a few bean chunks for texture. Use a little bean liquid or water if beans are too dry to mash.
Combine the beans, onion, cilantro, egg and sprinkle with salt and pepper.
Add cornmeal by the tablespoon until its made a batter that is barely stiff enough to handle. (You should be able to shape it with your hands without it sticking, but it should be quite fragile or the cakes will be dry.)
Add corn oil to a large, deep skillet and turn flame on medium. Shape the bean mixture into patties 2 to 3 inches across or into 1 ½ x 3 inch logs.
When the oil is hot, place them in the skillet. Don't crowd them; you may have to work in batches.
Cook the croquettes until nicely browned on all sides, adjusting the heat so they brown evenly without burning before turning, 7 or 8 minutes total. Keep warm in the oven or under aluminum foil until ready to serve, or serve at room temperature.
Garnish with salsa, fat-free sour cream and fresh cilantro sprigs, if desired. Brown rice with roasted or fresh corn make a nice accompaniment.
Note: as variations, you may add any of the following alone or together for extra zing in the batter: a dash of cumin, minced jalapeno, fresh chile, hot sauce or fresh squeezed lemon juice.
There are 322 calories in 1 serving of Black Bean Croquettes with Cornmeal.