My friend , Margarita, always makes them when she visits at my house. She boils the beans with salt and then fries them in lard at her house or uses canola oil at my house. She says to make sure the lard/oil is hot before putting the beans and pot juice in. She mashes with the back of a large cooking spoon. I have watched her do this many times but my beans are never as good as her's. I keep any leftovers in the freezer if she makes them.