Preheat the oven to 350 degrees.
Cut a lengthwise slit in each plantain and set it on a baking sheet. Bake until the flesh is thoroughly soft and oozing through the slit, 40 to 50 minutes, Set aside to cool.
Meanwhile, make the stuffing: Finely dice the poblano chile. Combine with beans, scallions,, cheeses, and pepper in a mixing bowl and stir to combine. The stuffing can be made up to a day in advance and reserved in the refrigerator.
Make the sough in a food processor or in a mixer with a paddle attachment: Peel, trim and discard any tough ends from the plantains. Combine the plantains, banana and salt and pulse until a smooth puree is formed, or mix until just blended. Be careful not to overwork the dough, or it will become too starchy. Wrap in plastic and chill about 2 hours.
To assemble the empanadas, roll 2 tablespoons of the dough lightly between your palms to form a ball. Line the bottom of a tortilla press with a small plastic bag and place the ball of dough in the center. Place another small bag over the dough and press to form a 3 1/2-inch circle. (If you do not have a tortilla press, the dough can be flattened with the palm of your hand on a counter, with a sheet of plastic above and below to prevent sticking). Place about 1 teaspoon of the bean stuffing on half of the dough circle and fold over to enclose, pressing the edges to seal. Place the stuffed empanadas on a platter and chill at least 30 minutes or as long as a day. (Stuffed empanadas can also be frozen).
To cook the empanadas, heat the peanut oil in a medium skillet over medium-high heat. Fry 4 to 6 empanadas, at a time, shaking the pan constantly, about 1 minute per side or until dark brown all over. (If they darken too quickly, as they may if very ripe plantains were used, lower the flame slightly). Drain on paper towels. Serve hot with Crema, Creme Fraiche or sour cream for dipping.
In large pot place beans and water and bring to a boil. Cover, reduce to a simmer and cook for 1 hour, or until tender and creamy in center. Crush the beans in their liquid with the potato masher or the back of a wooden spoon. In a large saucepan heat lard or oil over medium heat. Stir frequently, until the liquid evaporates and the beans form a creamy mass that pulls away from the bottom and sides of the pan, about 15 minutes cooking time. Serve immediately. Refried beans can be kept in the refrigerator 3 - 4 days and reheated in a covered casserole in a 350 degree oven.
c.1997, M.S. Milliken & S. Feniger, all rights reserved