In large heavy saucepan, heat oil over medium-high heat; cook onion, garlic, carrot, celery and mushrooms, stirring occasionally, for 15 minutes or until no liquid remains. Add stock, salt, pepper, nutmeg and bay leaf; cook, stirring occasionally, for about 5 minutes or until reduced by half.

Add tomatoes and tomato paste; bring to boil. Reduce heat and simmer for about 20 minutes or until thick enough to mound on spoon. Discard bay leaf. (Make-ahead: Refrigerate in airtight container for up to 24 hours; reheat to continue.)

Meanwhile, in large pot of boiling salted water, cook pasta for 8 to 10 minutes or until tender but firm; drain well and return to pot. Add sauce and toss to coat. Serve sprinkled with Parmesan cheese.