Heat about ½ inch vegetable oil in a large saute pan set over medium-high heat. Fry the plantain slices until golden brown on both sides. About 5 minutes.Set aside on a paper towel lined plate to dry.
Place two cups of corn flour in a mixing bowl.
Add a pinch of salt and mix through with clean dry hands.
Pour the water onto flour, mix well. As soon as the mixture is cool enough to handle knead together the flour and water until the mixture is thoroughly blended and there are no grainy lumps.If the dough is too soggy and sticks to your fingers add more flour. If it is too dry add water. The perfect dough should roll easily into a large ball without cracking.Divide the dough into 4 equal pieces and roll them into balls. Then pat it and turn it in your hands until its about half an inch thick and about 3-4 inches across. It should have the classic flying saucer shape now. Repeat with remaining balls.
Let the dough discs rest about 20 minutes.
Heat a little oil in a heavy frying pan or griddle and when hot add the arepas, as many as will comfortably fit in the pan. The idea is to give the arepas a crunchy exterior (“una cara”, literally a face, as they say in Venezuela) so don’t turn the heat up too high. When the arepas are brown on one side turn them over. The whole process should not take longer than 10 minutes.Preheat oven to 250 degrees.
Place arepas on a baking tray at the top of the oven, then lower the heat to 20
Bake 15 to 20 minutes. They should sound hollow when tapped with a knife when they are done.
Let them cool a couple of minutes then make an incision along the outer edge of each arepa. The trick is to slice through the middle but not going all the way – and then open it up like a pocket for the filling. Fill with the fried plantains, cheese and avocado slices.
