In a skillet over medium heat, brown the ground beef until no longer pink, about 5-7 minutes. Stir in the sofrito and tomato sauce, cooking for an additional 3-5 minutes. Add chopped pimento olives if desired, and season with salt and pepper. Allow the picadillo filling to simmer for 10 minutes.

While the filling simmers, peel and chop the potatoes into chunks. Boil in a pot of salted water for about 15-20 minutes until fork-tender. Drain and return them to the pot, mashing until smooth. Let the mashed potatoes cool slightly.

Take a scoop of the warm mashed potatoes and flatten it in the palm of your hand. Add a tablespoon of the picadillo filling to the center, then carefully fold the potato over it, sealing it tightly. Shape the mixture into a ball and repeat until all filling is encased.

In a deep pot or fryer, heat the oil over medium-high heat to 350°F. Use a thermometer to monitor the temperature.

Gently lower 3-4 croquettes into the hot oil, avoiding overcrowding. Fry for about 4-5 minutes, turning until golden and crispy. Use a slotted spoon to remove and let excess oil drain.

Serve the croquettes immediately while warm, optionally with a cilantro lime sauce or spicy dipping sauce.