Slice each mozzarella ball into two pieces and set aside.
Using a cheese grater, finely grate the onion.
In a large bowl, combine the milk, panko, Parmesan, ground beef, minced garlic, dried oregano, fresh parsley, egg, and grated yellow onion. Add about 1 teaspoon salt and 1/2 teaspoon pepper.
Knead the mixture with your hands until combined.
Measure out a scant 1 tablespoon of the mixture and gently form a ball. Press 1 mozzarella piece into the center and ensure the meatball mixture completely covers the mozzarella.
Repeat with all the meat mixture. You should get around 44–46 “mini” meatballs.
In a large nonstick skillet, add 1 and 1/2 tablespoons olive oil. Heat to medium-high and add in about half the meatballs. Gently turn the meatballs over and cook for about 3–4 minutes or until they are browned (but not cooked through). Remove to a plate.
Add another 1 and 1/2 tablespoons oil and repeat with the rest of the meatballs. Remove the rest of those meatballs to the plate.
In the same skillet, add remaining 1/4 cup olive oil. When the oil is hot, add the garlic.
As soon as the garlic sizzles, add the canned tomatoes. Pour 1 cup water into the can of tomatoes and slosh around to get the rest of the tomatoes. Pour that into the skillet as well.
Add red pepper flakes, oregano, and about 1 teaspoon salt. Stir.
Add 1 sprig of basil and submerge it in the sauce.
Add the cooked meatballs into the mixture and press to be covered in the sauce. Simmer for 8–12 minutes, turning every now and again, or until completely cooked through. Discard the basil sprig.
Meanwhile, prepare the pasta according to package directions. Drain.
Top the pasta with meatballs and sauce. Garnish with fresh ribboned basil, additional cracked pepper, and freshly grated Parmesan cheese.