Season the stew beef with salt and pepper.
Heat a large heavy bottomed skillet, such as cast iron, over medium heat. Add a teaspoon of oil to the pan.
When the oil is shimmering, add a single layer of stew meat to the pan. Brown on all sides. Add worcestershire sauce and stir to season all of the beef before transferring browned meat to a 5-6 quart slow cooker. You may need to work in batches to brown all of the meat, adding more oil between each batch if necessary.
Add the butter to the skillet and melt.
Add the mushrooms and onions to the skillet and cook for 5 minutes, stirring occasionally, until vegetables have softened.
Add the garlic to the skillet and cook for 1 minute more.
Transfer the vegetables to the crockpot with the meat.
Add the cream of mushroom soup to the crockpot and stir to combine.
Cover and cook on low for 8 hours or high for 4 hours, or until beef is tender.
Add the cream cheese to the slow cooker and stir until it has melted.
Stir in the sour cream until well combined and then add the cooked egg noodles and stir to coat.
Sprinkle with parsley before serving.