Season the steak cubes with salt and the crushed black peppercorns, pressing the pepper into the meat.
In a large pot, heat the olive oil over medium-high heat. Add the steak cubes and sear until browned on all sides, about 5-7 minutes. Remove the steak from the pot and set aside.
In the same pot, add the diced onion and sauté until translucent, about 3-4 minutes. Add the minced garlic and cook for an additional minute.
Pour in the beef broth and bring to a simmer. Return the seared steak to the pot and let it cook for 10 minutes.
Stir in the heavy cream, Dijon mustard, and Worcestershire sauce. Simmer for another 5 minutes until heated through. Adjust seasoning with salt if needed.
Serve hot, garnished with fresh parsley.