Prepare the filling: Heat the oil In a medium saucepan over medium-high. Saute the onion until translucent. Add the garlic, pepper, leeks, and scallions; cook 5 minutes. Stir in ground beef. Using a wooden spoon break the meat and season with salt and pepper to taste. Cook until it’s no pink, about 5 minutes. Add the tomato paste, wine, olives, and capers; mix well until everything is well combined. Adjust salt and pepper, if necessary. Reduce heat to low and simmer for 10-15 minutes, or until most of the liquid has evaporated. Remove from heat and set aside.
Prepare the sauce: In a small saucepan add the corn oil. Saute onion until transparent; about 3 minutes. Add the diced tomatoes and season with salt and pepper to taste. Cover and simmer for 20-25 minutes. Remove from heat and set aside.
Prepare the dough: Mix chicken broth and Harina PAN until has no lumps. Let stand for 5 minutes then add the corn oil and knead until smooth. Divide the dough into 14 equal-size balls. Set aside.
Assemble: Take a ball of dough and make a hole in the center with your finger, big enough to place the filling. Add 1-2 teaspoons of the filling. Close bringing the edges together carefully with your fingers. Re-form into a ball again. Repeat until all the dough is finish.
Cook: Fill a large pot halfway with water. Bring it to boil over medium heat high heat. At first boil reduce the heat to low. Place the stuffed dumplings in the hot water and cook about ten minutes. You’ll know when they ready because they’ll float. With a slotted spoon transfer them to a serving dish.
Top with tomato sauce and fresh cheese (queso fresco), if desired, and serve immediately.