Heat olive oil in a large skillet over medium heat. Add onion, carrots, and celery. Cook for 5 minutes until softened. Stir in garlic and cook another 30 seconds.

Increase heat to medium-high, add ground beef, and cook until browned. Break it up with a spoon. Drain excess fat if needed.

Stir in tomato paste, then add canned tomatoes, stock (or wine), oregano, basil, bay leaf, salt, pepper, and sugar. Mix well.

Reduce heat and simmer uncovered for 25 minutes, stirring occasionally. Remove bay leaf.

Cook spaghetti in salted boiling water until al dente. Drain.

Toss spaghetti with the sauce or spoon the sauce on top. Garnish with parsley and Parmesan.