In a 6 quart pot, on medium heat, add the olive oil, onions, garlic, dried basil, salt, and pepper. Saute for 5 minutes.
Add the crushed tomatoes, tomato sauce, and sugar. Stir to combine, then reduce the heat to medium-low and simmer the sauce while you move forward with making the meatballs. Make sure to stir your sauce every so often to make sure it doesn’t burn.
In a large mixing bowl add the ground beef, eggs, panko, parmesan cheese, fresh parsley, garlic powder, salt, and black pepper.
Using a large wooden spoon, mix all the ingredients together until well combined.Pro Tip: Be careful not to overwork the beef mixture because that causes tough meatballs.
Preheat your oven to 350°F. Prepare a rimmed baking sheet with a piece of parchment paper to cover the bottom. Set aside.
Using a kitchen scale, divide the meat mixture and weigh out 12 (5-ounce) meatballs. Shape your meatballs by lightly rolling them in your hands, then place the formed meatballs, in rows, on the prepared sheet pan.
In a large, heavy-duty skillet, heat the ¼ cup olive oil. Once the oil is hot, place 6 of your shaped meatballs into the skillet. You will brown your meatballs on all sides. This should take about 8 to 10 minutes. Once you have browned your meatballs on all sides, remove them from the skillet and return them to the baking sheet. Repeat this step with the remaining meatballs. When you are done, you should have 12 browned meatballs back on your parchment-lined baking sheet.
Place your baking sheet, with the browned meatballs, into the oven to finish baking the meatballs for 30 minutes.
Once you remove your cooked meatballs from the oven, place them into your pot of simmering sauce for another 30 minutes on medium-low heat.
Preheat your oven to BROIL. Line a rimmed baking sheet with aluminum foil and set it aside.
At this point, you can assemble your sub sandwiches by opening your sub roll lengthwise. Place 3 meatballs into each of the sub rolls. Top your meatballs with 2 slices of the deli sliced mozzarella cheese. Place your assembled meatball subs onto the aluminum foil-lined sheet tray and put them under the broiler for 2 to 3 minutes, or until your cheese has melted and your sub roll has crisped up slightly.
You can garnish your sub with a couple of spoonfuls of additional sauce, grated parmesan cheese, and chopped parsley if desired.