1. Wash the carrot and mushrooms. Peel and grate the carrot. Chop the mushrooms. Peel and chop the spring onion and garlic. In a bowl, mix the ground beef, vegetables, garlic, onion, breadcrumbs, grated parmesan, egg, parsley, salt, and pepper. Shape into meatballs.
2. In a pan, heat a drizzle of olive oil over medium heat and brown the meatballs. Pour in the tomato sauce and once it starts boiling, reduce the heat, cover, and let simmer for 15 minutes over low-medium heat.
3. Meanwhile, cook the spaghetti al dente in a pot of salted boiling water following the instructions on the package. Drain and return to the pot. Mix with a drizzle of olive oil. Season with salt and pepper. Divide the pasta among plates, then top with sauce and meatballs.