In a large skillet, cook the beef and onion over medium heat until meat is no longer pink; drain. Stir in the water, taco seasoning and salt. Reduce heat; simmer for 2-3 minutes.
Add mushrooms.
Sprinkle noodles over the top.
Pour tomato juice over the noodles and stir gently. Cover and simmer for 20-25 minutes or until noodles are tender.
Remove from the heat.
Combine sour cream and parsley; spread over the top. Cover and let stand for 5 minutes.