For the coulotte steak
- Prep the steak. Season the steak on all sides with sea salt and ground black pepper.
- Sear the steak. Heat a heavy-bottomed skillet over high heat for 1 minute. Add the avocado oil to the skillet and allow it to heat up for 30 seconds. Arrange the fillets in the pan and sear for 4 minutes. Flip the fillets.
- Melt the butter with herbs. Add butter, garlic, and rosemary to the skillet and allow the butter to melt (this should take about 20 seconds).
- Baste the steak. Tilt the skillet to gather all of the cooking juices and melted butter to one side and begin spooning the mixture over the steak (this is called basting). Continue to cook for another 6 minutes, continually basting. Flip again and cook for an additional 2 minutes, continually basting.
- Check the temperature. Insert a meat thermometer into the thickest part of the largest fillet. You are looking for 130-135 degrees F for a medium-rare steak. Continue to cook if the temperature is below 120 degrees F. (See steak doneness chart in my post.)
- Rest the steak. Once the steak has reached the proper internal temperature, transfer it to a cutting board and let rest for 5-10 minutes while you make the sauce. Do not remove the drippings, garlic, and rosemary. They will be used in the sauce.
For the mushroom sauce:
- Warm up the steak drippings. Heat the skillet (with all of the drippings, garlic, and rosemary) to medium-high heat and melt the butter.
- Add mushrooms. Add the mushrooms to the pan. Season with sea salt and ground black pepper. Sauté for about 5 minutes or until the mushrooms cook down to golden brown.
- Add wine. Pour the wine into the pan and continue to sauté until it evaporates. Lastly, remove the rosemary and garlic.
Transfer the steak to a serving platter and spoon the mushroom sauce over the fillets. Alternatively, you can cut the filets into 2-inch cubes and cover them in the sauce.