Preheat oven to 350°F. In a large skillet cook onion and garlic in 1 tablespoon of the olive oil for 8 minutes or until tender. Cool.
In a large bowl combine eggs, onion mixture, ground beef, 1 cup Grana Padano, the ricotta cheese, panko, parsley, basil, salt, and pepper. Mix to form a uniform mass and shape the mixture into 2-inch balls. Test one meatball before starting the next process. If the ricotta is too watery, add more breadcrumbs or ground beef. If it is too dry, add more ricotta.
Place meatballs on two parchment-lined 15x10x1-inch baking pans. Brush with the remaining 2 tablespoons olive oil. Bake 22 to 25 minutes or until 165°F.
In a very large skillet bring the marinara sauce to boiling. Add half of the meatballs to the skillet and simmer, uncovered, 5 minutes or until a nice saucy consistency. Garnish with Grana Padano, if desired, and serve over cooked pasta or on a hoagie roll to make these meatballs a meal.