Sauté chopped onion with vegetable oil, season with salt/black pepper. When the onions are almost translucent add minced garlic, cook for 2-3mins.
Then combine the rest of the red sauce ingredients thoroughly into a large heavy pot. Bring to a simmer over medium-high heat, stirring occasionally to prevent the sauce from sticking to the bottom of the pot.
Do this again for your Meatballs - Sauté your chopped onion with vegetable oil, season with salt/black pepper. When the onions are almost translucent add minced garlic, cook for 2-3mins. (You could do this once and just divide the onions/garlic in half for sauce/meatballs) Let onions/garlic cool down before adding it to a large mixing bowl.
Next, add the remaining meatball ingredients together in large mixing bowl using your hands to combine gently.
Using a Ice cream scooper, divide the meatball mixture into 25 - 30 even portions and roll into smooth meatballs. Place meatballs on a wire rack/cookie sheet with lip.
When all the meatballs are shaped, place them in the fridge for 20 mins to firmly mold together. Preheat oven to 400°
Roll the meatballs in flour and brown them on both side in a Sauté pan | Place in oven 400° for 25 mins. Then gently place the meatballs into the simmering sauce 1 at a time. Stir gently and continue to simmer for an additional 20 - 30 minutes.
Now slice a hoagie bun and then using your hands, remove some of the bread interior to form a hollowed-out pocket shape. Brush the inside of the hollowed out buns with the olive oil. Divide half the grated mozzarella evenly between the hoagie buns and bake, uncovered, until the cheese is melted and buns are lightly golden, about 3 - 4 minutes.
Remove from the oven and ladle some of the sauce into the buns. Place 2 or 3 meatballs inside each bun and top with more sauce. Divide the remaining mozzarella cheese among the tops of the buns and sprinkle with the Parmesan. Return to the oven and bake until the cheeses are golden brown, 4 - 6 minutes.
Bon Appétit :)
