Bring a large pot of salted water to a boil and cook the egg noodles according to package directions until al dente, then drain and set aside.
While the noodles cook, heat the olive oil in a large skillet over medium-high heat.
Season the beef strips with half of the sea salt and black pepper, then sear in the skillet for 2 minutes per side until browned but not fully cooked through; remove beef and set aside.
In the same skillet, add the sliced mushrooms and diced onions, sautéing for 5-7 minutes until the mushrooms are golden and onions are translucent.
Add the minced garlic and cook for 30 seconds until fragrant, then pour in the beef broth to deglaze the pan, scraping up any browned bits.
Reduce the heat to low and whisk in the Greek yogurt, Dijon mustard, and remaining salt and pepper until the sauce is smooth and thickened.
Return the beef and any accumulated juices to the skillet, tossing to coat in the sauce for 1-2 minutes until heated through.
Serve the beef and mushroom mixture over the cooked egg noodles and garnish with freshly chopped parsley.