Heat the olive oil in a medium saucepan over medium-low heat. Add the garlic and onions, and cook, stirring occasionally, until translucent and very soft, about 10 minutes.
Drain the black beans, and reserve 1/4 cup of the liquid. Add the beans, the reserved bean liquid, and the remaining ingredients, except the parsley, to saucepan; cover, raise heat to medium, and cook, stirring occasionally, 10 to 12 minutes. Remove from heat, transfer to a serving dish, and garnish with the parsley leaves. Serve immediately.