Step 1: Prepare the Meatballs

1. In a large bowl, combine the ground beef, breadcrumbs, Parmesan, egg, garlic, parsley, salt, pepper, Italian seasoning, and milk.
2. Gently mix with your hands or a spoon until just combined—avoid overmixing to keep the meatballs tender.
3. Shape the mixture into evenly sized meatballs, about 1 to 1.5 inches in diameter, and set aside.

Step 2: Brown the Meatballs

1. Heat 1 tablespoon of olive oil in a large skillet over medium heat.
2. Add the meatballs in a single layer, ensuring they aren’t overcrowded.
3. Cook for 2-3 minutes per side until browned, then transfer to a plate. They will finish cooking in the sauce.

Step 3: Make the Marinara Sauce

1. In the same skillet, add 2 tablespoons of olive oil and heat over medium heat.
2. Sauté the diced onion for 2-3 minutes until soft. Add the minced garlic and cook for 30 seconds until fragrant.
3. Pour in the crushed tomatoes and tomato sauce, then season with salt, black pepper, Italian seasoning, red pepper flakes (if using), and sugar. Stir well.
4. Reduce heat to low and let the sauce simmer for 10 minutes, stirring occasionally.
5. Stir in the fresh basil for an extra layer of flavor.

Step 4: Simmer the Meatballs in the Sauce

1. Gently place the browned meatballs into the simmering marinara sauce.
2. Cover and let them cook on low heat for 15-20 minutes, stirring occasionally.
3. Taste and adjust seasoning if needed.

Step 5: Cook the Spaghetti

1. Bring a large pot of salted water to a boil.
2. Add the spaghetti and cook according to the package instructions until al dente.
3. Drain the pasta and set it aside. Toss with a little olive oil to prevent sticking.

Step 6: Assemble and Serve

1. Divide the cooked spaghetti onto plates or a serving dish.
2. Top with meatballs and a generous amount of marinara sauce.
3. Garnish with grated Parmesan cheese and fresh basil or parsley.
4. Serve hot and enjoy!