In a medium saucepan, combine the beans, bay leaf, two onion quarters, smashed garlic, and enough water to cover by 2 inches, and bring to a boil. Reduce the heat so that the water boils gently and cook for 10 minutes. Cover, remove from the heat, and allow the beans to sit for 1 hour.
After 1 hour, return the beans to a low boil and cook, stirring occasionally, until they begin to soften, about 45 minutes. Add the salt and continue to cook until the beans are very tender, about 15 to 30 minutes longer. Drain the beans in a colander set over a bowl in the sink and reserve the cooking liquid. Discard the bay leaf, onion half, and garlic.
In a medium 10-inch skillet, heat the vegetable oil over medium-high heat. Add the chopped onion and cook until soft, stirring occasionally, about 4 minutes.
Add the minced garlic, cumin, and oregano, and cook for 1 minute.
Add the beans and 1 cup of the reserved cooking liquid and, using a potato masher, mash the beans until chunky-smooth. Add 3/4 cup more of the reserved cooking liquid and cook, stirring, until the beans are very thick and flavorful, about 10 minutes. Be careful of splatters! If the beans become too thick, simply add a little more of the reserved cooking liquid. When the beans have reached the desired consistency, stir in the olive oil and serve immediately. The beans are delicious on their own, or kick yours up by topping with any or all of the following optional items: grated cheese, chopped tomatoes, sour cream, and/or chopped chives.
Note: These beans can be made several days in advance and reheated before servingójust keep in mind that you may need to add a bit more liquid when reheating, as they tend to thicken as they sit and cool.