Bring a pot of water to a boil and cook the egg noodles according to package directions; drain and set aside.
Heat the olive oil in a large skillet over medium-high heat.
Add the beef sirloin strips to the skillet, seasoning with half of the sea salt and black pepper, and sear until browned on all sides.
Remove the beef from the pan and add the sliced mushrooms and diced onions, sautéing until the mushrooms are golden and onions are translucent.
Stir in the minced garlic and cook for 30 seconds until fragrant.
Pour in the beef broth, Dijon mustard, and Worcestershire sauce, scraping the bottom of the pan to release the flavorful browned bits.
Reduce heat to low and simmer for 3 to 5 minutes until the liquid has slightly reduced.
Stir the cooked beef and egg noodles back into the skillet.
Remove the pan from the heat and fold in the plain Greek yogurt until the sauce is smooth and creamy.
Season with the remaining sea salt and black pepper, then garnish with chopped fresh parsley before serving.