Cook beef in a large, nonstick skillet over medium heat. Stir thoroughly to break up meat until no longer pink, for about 5 minutes.
Add onion, celery, carrot and bay leaf; cook, stirring often, until vegetables are tender, for about 6 minutes.
Add cream and marinara sauce; simmer until sauce is thickened slightly, for about 3 minutes. Season with salt and pepper.
Meanwhile, boil a pot of salted water and cook tortellini per package directions. Drain, add pasta to sauce, and toss well. Top with Parmesan cheese if desired.