Bring a pot of salted water to a boil and cook the egg noodles according to package instructions until tender, then drain and set aside.
Slice the top sirloin into thin strips and season lightly with a portion of the sea salt and black pepper.
Heat the olive oil in a large skillet over medium-high heat and sear the beef strips until browned on both sides, then remove them from the pan and set aside.
In the same skillet, add the diced onions and sliced mushrooms, sautéing until the vegetables are soft and the mushrooms have developed a deep golden color.
Add the minced garlic and cook for 30 seconds until fragrant, being careful not to burn it.
Pour in the beef bone broth and whisk in the Dijon mustard, using a wooden spoon to scrape up any browned bits from the bottom of the pan.
Reduce the heat to low and stir in the Greek yogurt until the sauce is smooth and creamy.
Return the beef to the skillet and simmer for 2-3 minutes until the sauce has thickened slightly.
Stir in the cooked egg noodles, season with the remaining sea salt and black pepper, and toss until everything is well coated.
Garnish with freshly chopped parsley and serve immediately.