1. Pat the ribeye steaks dry with paper towels and season both sides generously with salt and freshly ground pepper. Let them rest at room temperature for 20 minutes.

2. Heat olive oil in a heavy skillet over medium-high heat. Once hot, add the steaks and sear for 3-4 minutes per side for medium-rare, or longer if desired. Add 1 tablespoon of butter during the last minute and baste the steaks. Transfer steaks to a plate and cover loosely with foil.

3. In the same pan, reduce the heat to medium. Add the remaining 1 tablespoon of butter and minced garlic. Sauté until fragrant, about 1 minute.

4. Pour in the beef broth and simmer for 2 minutes, scraping up browned bits from the pan.

5. Stir in the heavy cream, Dijon mustard, and optional rosemary. Simmer until the sauce thickens slightly, about 3-4 minutes. Taste and adjust seasoning.

6. Return the steaks to the pan and spoon sauce over the top. Let them warm for a minute, then garnish with fresh parsley before serving.