For the refried black beans: Heat the oil in a separate medium saucepan over medium-high heat. Add the onions and cook, stirring occasionally, until they are softened and translucent, 6 to 7 minutes. Stir in the garlic, ancho chile powder, oregano, 1 teaspoon salt and a few grinds of black pepper and cook, stirring, until the garlic is fragrant, about 1 minute. Add the black beans and 3/4 cup water and bring to a boil. Reduce the heat to medium-low and simmer, stirring occasionally, until the beans are heated through, about 5 minutes.
Continue to heat while gently mashing the beans with a wooden spoon, potato masher or fork until the mixture is thickened and only a few chunks of whole beans can be seen, about 5 minutes. Remove from the heat and stir in the sour cream. |