I use the term well-fried beans instead of re-fried beans because as the name suggests you actually have to spend some time frying them in pork lard for them to acquire that amazing taste that is characteristic of this dish.
This is a two step recipe. First you need to boil the beans.
1 lb black beans
11/2 to 2 quarts, hot water
1/2 cup white onion, roughly chopped
2 tbsp pork lard
salt to taste
2 sprigs of fresh epazote
Place beans on a flat tray and pick any stones or visible debri. Rinse the beans in cold water to make sure any dirt is removed. Place beans into a pot and cover with the hot water. Add the onion and lard and bring to a boil, lower the heat and let them simmer covered, until they are soft about 3 hours. add salt and let simmer for another half hour until the beans are very soft. add the epazote sprigs before the end of the cooking time, as the epazote as well as any other fresh herb, tends to lose flavor if cooked too long.
6 tbsp pork lard
2 tbsp finely chopped white onion
1/2 lb black beans cooked
In a heavy-bottomed hot skillet, heat the pork lard and fry the onions, until soft, without browning. Start adding one cup of the beans with their liquid and mash them well as you cook them, over high heat (becareful because they splatter). add the rest of the beans one small batch at the time and keep mashing until you have a rough paste. when the puree sizzles at the edges, the beans are ready to use. incorporate them to your favourite recipes or eat them on their own with fresh tortillas.
If the puree becomes to dry, add a little more of the cooking liquid and incorporate well