Whisk together the broth, flour, tomato paste, onion soup mix, 1 teaspoon salt and ½ teaspoon pepper in a medium bowl until combined.
Add to a 6-quart slow cooker and top with the mushrooms and chicken.
Cover and cook on high for 4 hours.
When ready to serve, bring a large pot of water to a boil; salt the water generously.
Add the noodles and cook until al dente according to the package directions.
Drain and toss in a large bowl with the butter until the butter is melted and the noodles are completely coated.
Transfer the chicken to a small bowl and shred with 2 forks.
Whisk the cream cheese into the sauce until completely incorporated; stir in the chicken and noodles.
Top with parsley before serving.
