Preheat your oven to 400°F.
Remove the filet mignon steaks from the fridge. Pat them dry with paper towels and season both sides generously with salt and black pepper. Let them rest on a plate at room temperature for 30 minutes before cooking.
While the steaks are resting, make the garlic and herb butter. In a small bowl, mix together the butter, garlic, parsley, thyme, and rosemary.
Heat a cast iron skillet over medium-high heat (if you’re going to use a nonstick skillet, see notes)**. Once hot, add the olive oil and swirl to coat the bottom of the pan.
Once the oil is hot, place the steaks in the skillet. Sear for about 2-3 minutes on the first side, and 2 minutes on the second side, or until a golden-brown crust forms. Next, use tongs to roll them on their sides in the skillet for 1 minute to get a golden-brown crust on the edges, too.
Transfer the skillet to the preheated oven and bake for about 5-6 minutes for medium-rare, or until the internal temperature reads 125°F on an instant read meat thermometer, keeping in mind that there will be some carryover cooking as the steak rests. Adjust the time if you prefer your steak more or less done. Keep in mind that it’s recommended to cook steaks to an internal temperature of 145°F, but individual preferences vary. See the blog post above to learn how to use the finger test to check the doneness of your steak quickly and easily. See the notes below for different levels of doneness.
Remove the skillet from the oven and top each steak with a dollop of the herb and garlic butter. Tent with aluminum foil and let the steaks rest for 5 minutes before serving. This allows the juices to redistribute and the butter to absorb into the steak.