01 - Remove the filet mignon steaks from the refrigerator 30 minutes prior to cooking to allow them to reach room temperature. Pat the steaks thoroughly dry with paper towels.
02 - Preheat your oven to 400°F. Generously season both sides of the steaks with kosher salt and freshly ground black pepper.
03 - Heat olive oil in a heavy, oven-safe skillet (such as cast iron) over medium-high heat. Once hot, sear the steaks for 2–3 minutes per side until a rich, golden crust forms.
04 - Add butter to the skillet. As it melts, spoon the butter over the steaks. Transfer the skillet directly to the preheated oven and roast for 5–7 minutes for a medium-rare doneness (internal temperature of 130°F), or adjust to achieve your preferred level of doneness.
05 - Carefully remove the skillet from the oven. Transfer the cooked steaks to a clean plate, tent them loosely with aluminum foil, and allow them to rest for 5 minutes. This is crucial for juicy results.
06 - While the steaks are resting, combine balsamic vinegar, honey, and the optional chopped rosemary in a small saucepan. Bring the mixture to a gentle boil over medium heat, then reduce the heat to a simmer. Cook for 6–8 minutes, stirring occasionally, until the reduction thickens and reduces by approximately half, becoming syrupy.
07 - Plate the rested filet mignon steaks. Generously drizzle the warm balsamic reduction over each steak. Garnish with fresh rosemary sprigs or microgreens if desired, and serve immediately.