Add onions, garlic, meat, broth, Worchestershire sauce, and seasonings to slow cooker.
Cover and cook on high for 4 hours or low for 7.
30 minutes before cooking time has finished, add the mushrooms and sour cream. Stir until the sour cream is fully mixed in.
In a small bowl, mix together the arrowroot powder and cold water and add.
Make the pasta according to package directions.
Once the soup has finished cooking, drain the pasta and add it to the soup.
Mix well and serve!