Cut the ends of plantains and then cut them into 2-3 pieces with the skin on. Boil in salted water for 20 minutes or until the soften
Remove from water and peel the plantain. Puree the pieces using a potato ricer.
Add the oil, salt, and pepper to the pureed plantains. Mix well with a spoon. Let this mixture cool for a few minutes before adding the egg and flour
Add the egg yolk and mix until completely combined. Add the flour and knead with your hands until the dough comes together
On a floured surface, using a rolling pin, roll dough into a large rectangle. Using a round cookie cutter, cut out circles. Repeat the process with remaining dough
Place the circles on the sheet pan
Cut the cheese into rectangles and place them on the lower half of the plantain circle. Fold the circles into a semi-circle shape and use a fork to crimp the edges making sure they are completely closed
Brush the tops of the empanadas with the beaten egg and bake for 15-20 minutes or until browned on top