Sort the black beans, discarding any stones or damaged beans.
Wash the black beans in a colander and then, soak them in three times their volume of cold water for at least 4 hours or best, overnight (12 hours or more) so they will become more tender and cook faster. Rinse and drain them. Reserve.
Cook the black beans: In a large, heavy-bottom pan over medium-high heat, bring the black beans with 6 cups of water and 1 tablespoon of oil to a boil. Oil reduces foaming during the cooking process! Then, cover the pan and reduce heat. Let simmer over low heat for 60 to 90 minutes or until almost tender. Remove from heat and reserve, covered.
If cooking black beans in a pressure cooker (something very common in Brazil), make sure the pot is no more than half full of ingredients, including water. Soaked beans may be cooked in about 20 minutes while unsoaked beans generally take 25 to 30 minutes and so to cook depending on how old the beans are. The truth is the older the beans, the more cooking time required.
In a separate pan, heat the oil over medium heat and cook the diced onion until translucent, stirring occasionally. Next, add the garlic and cook for about 30 to 60 seconds, stirring occasionally.
Mix the cooked onion and garlic into the cooked black beans. Add the bay leaves, and stir in all the seasonings, spices, and the vinegar (While vinegar improves taste and reduces gassy elements, it should be added near the end of the cooking time because it may toughen the skins).
Add 1/2 to 1 cup of water more, only if necessary. Cover and let simmer over medium-low heat for additional 15 minutes or until tender (If black beans were cooked in a pressure cooker, add those ingredients and let simmer for 5 to 10 minutes, uncovered).
Stir and remove the bay leaves. If desired, remove about 1 cup of cooked black beans (grains and broth) and blend in a blender until smooth. Add back to the cooked beans and stir. This will make the beans thicker and tastier. Right before serving, sprinkle the chopped cilantro or parsley if desired.
Black beans can be served with white rice (a staple in Brazil) and your favorite meat, or used as a base for black bean soup and dips.