Serve with Zarape De Pato. Epazote is similar to, and can be replaced with, chopped fresh cilantro.
Bring beans and the water to a boil in a medium saucepan over medium-high heat. Reduce heat; simmer until tender, about 1 hour. Add epazote, garlic, and salt; cook until beans are very soft, about 15 minutes. Set aside to cool in liquid.
Working in batches, puree beans (including garlic) in a food processor to form a fairly smooth paste, adding cooking liquid as needed. Heat oil in a large saute pan over medium-high heat. Add bean puree; cook, stirring, until the oil is incorporated, about 5 minutes. Serve hot.