Peel the plantains and slice them diagonally into 1/2-inch thick slices.
In a mixing bowl, combine the all-purpose flour, cornstarch, sugar, salt, and baking powder.
Add the water and vanilla extract, mixing until you get a smooth batter. The batter should be thick enough to coat the plantain slices but still pourable. Add more water if necessary.
In a deep skillet or frying pan, heat about 2 inches of vegetable oil over medium heat until it reaches 350°F (175°C).
Dip each plantain slice into the batter, ensuring it is well coated.
Carefully place the coated plantain slices into the hot oil, frying them in batches to avoid overcrowding the pan.
Fry for about 2-3 minutes on each side, or until the plantains are golden brown and crispy.
Use a slotted spoon to remove the fried plantains from the oil and drain them on paper towels.
Enjoy your meal!