Bring a small pot of salted water to a boil and cook the chickpea pasta according to package directions until al dente, then drain and set aside.
While the pasta cooks, slice the beef sirloin into thin strips and season with half 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, about 2 minutes per side, then remove from the pan and set aside.
In the same skillet, add the diced onions and sliced mushrooms, sautéing until the mushrooms are tender and the onions are translucent.
Add the minced garlic and cook for 30 seconds until fragrant.
Pour in the beef broth and Dijon mustard, scraping the bottom of the pan to release the browned bits, and simmer for 2 minutes.
Reduce the heat to low and stir in the Greek yogurt, remaining salt, and pepper until the sauce is smooth and creamy.
Add the cooked beef and pasta back into the skillet, tossing gently to coat everything in the sauce.
Garnish with freshly chopped parsley and serve immediately.