In a large skillet, heat olive oil over medium-high heat. Add the beef cubes and season with salt and pepper. Sear until browned on all sides, about 5 minutes. Transfer the beef to the slow cooker.
In the same skillet, add the chopped onion and minced garlic. Sauté for 2-3 minutes until softened. Add the sliced mushrooms and cook for an additional 3-4 minutes. Transfer the vegetable mixture to the slow cooker with the beef.
Pour in the beef broth, Worcestershire sauce, dried thyme, and paprika, stirring to combine all ingredients well.
Cover the slow cooker and cook on low for 7-8 hours or on high for 4-5 hours, or until the beef is tender.
About 30 minutes before serving, in a small bowl, whisk together the sour cream and flour until smooth. Gradually stir it into the slow cooker to thicken the sauce. Adjust seasoning with additional salt and pepper if needed.
Cook your egg noodles or rice according to package instructions. Serve the beef stroganoff over noodles or rice, garnished with fresh parsley.
Notes
Serve with egg noodles or rice, and garnish with fresh parsley.