In a large bowl, mix bread crumbs and milk, and allow to sit and adsorb
Heat olive oil in a skillet over medium heat. Add onion; cook and stir until onion has softened and turned translucent, about 5 minutes.
Reduce heat to low and continue cooking and stirring until onion is very tender, about 15 minutes more.
Once bread crumbs have adsorbed milk, add beef and pork to bowl and mix.
Add onions, bread crumb mixture, eggs, Parmesan cheese, parsley, garlic, salt, black pepper, basil, oregano, thyme marjoram rosemary, and red pepper flakes; mix together using a rubber spatula until combined.
Cover and refrigerate.
Make Sauce
While meatball mix is chilling, add olive oil to heavy bottomed pot and heat until shimmering, Then add diced onion, carrot, and cook until onion is translucent and vegetables are soft.
Add minced garlic, cook for 30 seconds or until fragrant.
Add tomato paste and cook until paste starts to darken and caramelize, about 5 minutes.
Add tomato sauce, diced tomatoes, red pepper flakes, basil, oregano, thyme, marjoram, rosemary, and Worcestershire sauce.
Cook, simmering, while preparing and cooking meatballs.
Cook Meatballs
While sauce is simmering, preheat oven to 425 °F.
Form mixture into balls about 1 ½ inches in diameter; arrange in a single layer on baking sheet.
Bake in preheated oven until browned and cooked through, 15-20 minutes.
Once browned, add meat balls into pot with sauce along with any accumulated juices. Allow to simmer for 5 minutes