Place potatoes into a large pot; cover with salted water. Bring to a boil over high heat, then reduce heat to medium-low, cover, and simmer until tender, about 20 minutes. Drain and allow to steam dry for 1 to 2 minutes. Mash potatoes with 1/2 teaspoon salt in a bowl until no lumps remain. Set aside to cool to room temperature.

Meanwhile, heat vegetable oil in a large skillet over medium heat. Cook and stir green pepper, onion, and garlic in the hot skillet until onion has softened and turned translucent, about 10 minutes.

Increase heat to medium-high; stir in ground beef. Cook and stir until beef is crumbly and no longer pink. Stir in tomato paste, vinegar, cumin, 1 teaspoon salt, and pepper until tomato paste has dissolved. Transfer beef mixture to a bowl; allow to cool to room temperature.

Line a baking sheet with plastic wrap or waxed paper; set aside. Beat eggs in a mixing bowl; set aside. Pour bread crumbs and flour into separate, shallow dishes; set aside.

Grab a handful of mashed potatoes (about 1/12 of the mashed potatoes); split into 2 equal portions. Form each piece into a small bowl shape and fill each with beef mixture. Place halves together, seal edges, and smooth to make a round ball. Repeat this step with remaining potatoes and beef mixture.

Working one at a time, gently roll potato balls in flour to coat; shake off excess. Dip into beaten egg, then roll in bread crumbs. Gently toss between your hands so any bread crumbs that haven’t stuck can fall away. Place breaded potato balls onto the prepared baking sheet. Refrigerate for 2 to 4 hours or freeze for later use.

Heat oil in a deep fryer or large saucepan to 350 degrees F (175 degrees C).

Cook potato balls in hot oil in batches, using tongs to roll balls around as they cook to ensure even browning, until crispy and golden brown, about 3 minutes per batch. Drain on a paper towel-lined plate.