Cook the Spaghetti: Bring a large pot of salted water to a rolling boil. Add the spaghetti and cook until just tender, yet firm to the bite (al dente). Drain the pasta thoroughly and set aside.

Prepare the Meatballs: In a spacious mixing bowl, combine the ground beef, bread crumbs, finely chopped parsley, grated Parmesan, minced garlic, egg, 1 teaspoon of salt, and the red pepper flakes. Gently mix the ingredients together until they are well incorporated, being careful not to overwork the meat. Shape the mixture into 16 evenly sized meatballs.

Brown the Meatballs: Heat the olive oil in a large pot over medium heat. Once the oil is hot, add the meatballs in a single layer. Cook them, turning occasionally, until they are browned all over, which should take about 10 minutes. Once browned, remove the meatballs from the pot and set them aside on a plate.

Make the Sauce: In the same pot, add the finely chopped onion and sauté until it softens, about 5 minutes. Stir in the crushed tomatoes and add the bay leaf. Season the sauce with salt and freshly ground black pepper. Bring the sauce to a gentle simmer.

Simmer the Meatballs: Return the browned meatballs to the pot, submerging them in the tomato sauce. Cover the pot and allow the sauce to simmer until it thickens, approximately 8 to 10 minutes.

Serve: Plate the spaghetti and generously spoon the meatballs and sauce over the top. Garnish with an extra sprinkling of freshly grated Parmesan before serving.