Prepare slow cooker by greasing or spraying interior with non-stick oil. Add stew meat, then top with onion, salt, pepper, garlic powder, onion powder, garlic and Worcestershire sauce. Stir well mix seasonings in with meat. Add 2 cups beef broth, stir and cook covered on low for 8 hours.
At the 8 hour mark, in a medium size bowl combine remaining 1/2 cup of beef broth with corn starch, and mix well, until all cornstarch is dissolved and incorporated into broth. Scoop out a few spoonfuls of the hot liquid from the slow cooker, and add it to the cornstarch and broth mixture, stir to combine. To that mixture add sour cream and cream cheese and mix until combined and smooth. Spoon the mixture into slow cooker, and stir to combine with ingredients in slow cooker. Place lid back onto slow cooker and allow to cook for 20 minutes.
During that final 20 minutes cook time, cook pasta according to package directions for a dente pasta. Take care not to overcook pasta. Drain, but do not rinse pasta. Add cooked pasta to the slow cooker and gently stir to combine. Serve immediately, topped with salt and pepper to taste, and fresh parsley or thyme for garish, if desired.