The first thing you will need is Picadillo, it doesn't matter whether you use Carne (beef) or Cerdo (pork).
Here is my recipe for it: https://youtu.be/-J_D64ByeSc
While your cooking the Picadillo go ahead and make mashed potatoes. You want to make them thick as possible, so decrease the liquids you would normally use to make them.
Beat one egg and mix it into the Mashed Potatoes.
Form the Mashed Potatoes into balls, making an indentation in the ball. Fill the indentation with Picadillo then then cover back up. Make sure to put plenty of Picadillo as you don't want them to come out too starchy.
Once all are formed beat the other two Eggs, fill a medium bowl half way with Corn Starch/Bread Crumbs. Brush each Relleno de Papa with the egg wash and run through the breading.
Heat Oil to 350 degrees.
Place Relleno de Papas into the oil, it should only take a couple of minutes for them to come out a golden brown.