Sort through beans, removing any stones and dirt. Place beans in a large colander and rinse very well under running water.
Transfer beans to a 3-quart slow cooker. Add water and bay leaf.
Turn slow cooker to high and cook for 10 to 12 hours. See note #4.
All slow cookers cook differently, but you can determine how long your beans need to cook by testing them. If they are very soft, tender, and starting to fall apart, they are done. But it doesn’t hurt to cook them longer than needed; provided they have sufficient water, it’s difficult to overcook beans.
When beans are done, remove bay leaf.
Finely dice onion.
Sauté onions in a medium saucepan (3- to 4-quart) over medium-low heat for 2 minutes or until they begin to soften.
Reduce heat to low and continue sauteing for 8 minutes or until onions are translucent and lightly browned.
Add minced garlic and continue sautéing for 1 to 2 minutes.
Meanwhile, carefully pour off and reserve most of liquid from beans. Set aside.
Add seasonings to beans. Using a potato masher or a large fork, mash beans adding in as much reserved bean liquid as needed until desired consistency is reached.
When onions and garlic are done, stir into mashed beans.Serve warm or cold.
Notes
1. It is important that the beans come to a boil during cooking. Most slow cookers get hot enough to bring beans to a good boil for several hours. Make sure your slow cooker gets hot enough by checking your beans at the end of the cooking time to see if they are gently boiling.2. All slow cookers cook differently. Some lose a lot of steam during cooking while others do not. Adjust water amount accordingly.3. This recipe is for a 3-quart slow cooker. If using a larger slow cooker, you can increase ingredient amounts. If doubling the recipe, you will only need 12 to 14 cups water.4. The cooked beans should be very, very tender before serving. If your beans are not soft after 8 hours of cooking, they may be too old or your slow cooker may not be working correctly.