To make the meatballs: Place the ground beef and pork in a large bowl. Add onions, garlic, scallion, red bell pepper, masarepa, egg, salt and pepper. Mix well using your hands.
Form the meatballs and place them on a platter.
Place the oil in a large saucepan over medium heat. Sauté the meatballs until well-browned on all sides, about 7 minutes total. Remove the meatballs to a platter lined with paper towels.
To make the sauce: Sprinkle in the flour and stir with a wooden spoon to dissolve into the fat. Pour in the beef broth, and stir with a wooden spoon to loosen the bits from the bottom of the pan. Simmer and stir until the liquid is reduced and a sauce starts to form. Season with salt and pepper.
Add the hogao and cook for 10 minutes, stirring often. Return the meatballs to the sauce. Simmer until the sauce thickens slightly and the meatballs are heated through, about 15 to 20 minutes.