Heat oil in large saucepan over medium heat. Saute onion and garlic until golden, about 5 minutes. Add beans, vegetable stock, cumin, coriander seeds, and salt and pepper to taste. Reduce heat to medium-low and cook for about 15 minutes, or until aromatic.
Meanwhile, slice each plantain in half lengthwise, and peel off skin. Heat enough oil for frying in large skillet. Fry plantain halves until golden on one side, turn over, and continue frying until golden. Remove from heat and place on paper towels to absorb extra oil.
To serve, place plantain halves on each plate. Spoon beans over plantains, or, alternatively, place scoop on the side. Top each serving with 2 tablespoons of salsa, 2 tablespoons of sour cream, and sprinkling of cilantro.
*You can heat up this dish with a few dashes of hot sauce or some diced jalapeno chiles.