1. Mix together the hot mashed potatoes, eggs, butter and 2 teaspoons of cornstarch. Set aside and let cool.
2. In a frying pan, heat the olive oil. Add the ground beef and cook until no longer pink. Stir to break up the meat.
3. Add the sofrito, tomato sauce, oregano and salt to the cooked ground beef. Mix thoroughly. Turn the heat to low and simmer for 30 minutes. Remove from heat and allow to cool.
4. Spread a spoonful of the potato dough mix in the palm of your hand. Make an indentation in the middle and stuff it with the meat mixture.
5. Cover the filling with more potato dough. Shape into a ball. Dust the ball lightly with the remaining cornstarch.
6. Repeat until mix is used up.
7. Deep fry the stuffed potato balls until golden (about 2 minutes).
8. Remove and drain on paper towels.
Servings: Makes 12 to 16 potato balls.