Pat beef chuck strips completely dry with paper towels. Season evenly on all sides with garlic powder, onion powder, sea salt, and black pepper.

Heat olive oil in a large skillet over high heat. Sear the beef strips in batches for 2 to 3 minutes until a golden-brown crust forms. Transfer seared beef into a 6-quart oval slow cooker.

In the same skillet, quickly sauté the diced onion and minced garlic for 2 minutes to lift any caramelized fond from the pan. Transfer onions, garlic, and sliced cremini mushrooms into the slow cooker.

Pour in the beef bone broth, Worcestershire sauce, and Dijon mustard. Add dried thyme. Stir gently to combine everything.

Cover with the lid and cook on LOW for 7 to 8 hours (or on HIGH for 4 to 5 hours) until the beef chuck is melt-in-your-mouth fork tender.

Whisk cornstarch and cold water in a small cup until smooth. Pour into the slow cooker and stir well. Cover and cook on HIGH for 20 to 25 minutes until the gravy thickens and turns glossy.

Switch the slow cooker to WARM or OFF. In a medium bowl, whisk the softened cream cheese and sour cream with a ladle of warm broth from the slow cooker until silky smooth. Stir this velvety mixture back into the slow cooker until fully incorporated.

Stir in fresh chopped parsley. Taste and season with additional sea salt or black pepper if desired.

Boil egg noodles according to package instructions, drain, and toss with 2 tbsp melted butter. Spoon generous mounds of creamy beef stroganoff over warm egg noodles and serve piping hot!