In a large mixing bowl, combine ground beef, breadcrumbs, egg, minced garlic, parsley, and Parmesan cheese. Mix gently until just combined, then form into 1-inch meatballs and place on a baking sheet.

Preheat your oven to 400°F (200°C). Bake the meatballs for 20 minutes until browned and cooked through.

In a skillet, heat olive oil over medium heat. Add diced onion and sauté for 5 minutes. Stir in crushed tomatoes and Italian seasoning, simmer for 10 minutes.

Add the baked meatballs to the sauce, let them simmer together for an additional 5 minutes.

In a pot of boiling salted water, cook spaghetti according to package instructions, usually around 8-10 minutes for al dente. Drain and reserve pasta water.

Plate spaghetti with sauce and meatballs, garnish with fresh basil and extra Parmesan.