2. Cut a lengthwise slit into each plantain and set on a baking sheet. Bake until the flesh is thoroughly soft and oozing through the slit, 40 to 50 minutes. Set aside to cool.
3. Meanwhile, make the stuffing: Finely dice the poblano chile. Combine with the remaining stuffing ingredients in a mixing bowl and stir to combine. The stuffing can be made up to a day in advance and reserved in the refrigerator.
4. Make the dough 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 for about 2 hours.
5. 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.)
6. 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, leaving the remaining oil in the pan. Serve hot with Crema, or sour cream for dipping.