In a large bowl, combine the yellow cornmeal, warm water, salt, and vegetable oil. Mix until a smooth dough forms. Cover and let rest for 10 minutes.

Boil the diced potatoes in a pot of salted water until tender, about 10 minutes. Drain and mash with the butter until smooth.

In a skillet, cook the ground beef over medium heat until browned, breaking it into small pieces. Add the chopped onion, garlic, cumin, paprika, salt, and pepper. Cook for another 5-7 minutes until the onion is softened.

Mix the mashed potatoes with the cooked beef mixture to create the empanada filling.

Take a small portion of the cornmeal dough and flatten it into a thin circle using your hands or a tortilla press.

Place a spoonful of the filling on one half of the dough circle. Fold the other half over the filling to create a half-moon shape. Press the edges together firmly to seal.

Heat vegetable oil in a deep skillet over medium-high heat. Fry the empanadas in batches, turning occasionally, until golden brown and crispy, about 3-4 minutes per side.

Drain the empanadas on paper towels and serve warm with ají sauce or lime wedges.