Preheat oven to 400°F. Line a baking sheet with parchment paper; set aside.

Using a medium bowl, combine the bread crumbs and milk; let soak for 5 minutes.

Meanwhile, add the olive oil to a medium frying pan and place over medium-high heat. Once hot, add the diced onions and cook for 6-7 minutes, or until onions begin to soften.

Transfer onions and soaked bread crumbs into a large mixing bowl. Add all of the remaining meatball ingredients (beef, pork, egg, parsley, garlic, salt, pepper, oregano, red pepper and Parmesan cheese). Mix until just combined. (Tip: Take care not to overmix or the meatball may be tough.)

Shape mixture into 1½” balls and place meatballs 1” apart on prepared baking sheet.

Bake for 18-22 minutes, or until meatballs are no longer pink in the center.

While the meatballs are baking, cook spaghetti according to package instructions. Drain and toss with a bit of milk to keep pasta from sticking together; set spaghetti aside.

Using a medium saucepan, add olive oil and place over medium-high heat. Once hot, add onions and cook for 5 minutes, stirring occasionally.

Add the garlic, crushed tomatoes, parsley, salt and pepper. Reduce heat to medium-low and continue cooking for 20 more minutes, stirring occasionally.

To serve, divide the spaghetti onto plates and top with meatballs and sauce.

{Optional} Garnish with additional fresh parsley and grated Parmesan cheese before serving.