Sort the beans on the counter and rinse until the water runs clear.
Combine beans, water, onion, garlic, and fat in a large pot. Boil for 5 minutes.
Reduce heat to the lowest simmer, with the lid tilted. Simmer for 1.5–2.5 hours, topping up with hot water only.
Add salt at about the 1-hour mark.
Cook until a bean crushes with no resistance.
For refritos: Heat 3 tbsp manteca in a wide pan over medium heat.
Cook half an onion, chopped fine, until soft and golden.
Lift the beans into the pan with a slotted spoon, followed by some broth. Let them sizzle for a minute, then mash.
Control texture with ladles of bean broth.
