01 - Combine softened butter with minced garlic, chopped parsley, chives, thyme leaves, lemon zest, and a pinch of salt in a small bowl. Mix thoroughly until all ingredients are evenly distributed. Shape the mixture into a log using parchment paper and refrigerate until firm, approximately 30 minutes.
02 - Remove filet mignon steaks from refrigeration 30 minutes prior to cooking to reach room temperature. Pat both sides dry with paper towels to remove excess moisture. Generously season both sides with kosher salt and freshly ground black pepper, pressing seasoning into the meat.
03 - Heat olive oil in a heavy cast iron skillet over medium-high heat until the oil begins to smoke slightly, indicating proper temperature for searing.
04 - Place seasoned steaks in the hot skillet. Sear for 3 to 4 minutes on the first side until a deep brown crust forms. Flip using tongs and sear the second side for an additional 3 to 4 minutes for medium-rare doneness. Use tongs to hold steaks vertically and sear the fat edges for 30 seconds to 1 minute.
05 - Transfer steaks to a clean plate and tent loosely with aluminum foil. Allow the meat to rest for 5 minutes to let juices redistribute throughout the steak.
06 - Remove the chilled garlic herb butter from the refrigerator and slice into rounds. Place a generous pat of butter on each hot steak, allowing it to melt over the meat. Serve immediately.