| 1 |
Rinse beans and sort for debris. Place in a large bowl and cover with cold water to soak at room temperature for at least 12 hours. |
| 2 |
Drain the beans. Place the beans along with the onion in a 3 qt pan and add enough water to cover by 1 inch. Cover and bring to a boil. Reduce heat and simmer until beans are very tender and mash easily (about 2 1/2 hours). Add water as needed to keep from boiling dry. |
| 3 |
Drain, reserving 1 cup of the liquid. With a potato masher, or in a blender or food processor, mash the beans until coarsely chopped. Add the reserved liquid as needed to make a past-like consistently. Stir in the butter. |
| 4 |
Return all to the pan and cook, stirring constantly, over medium heat until fat is absorbed and beans are very hot. Season with the salt. |