Remove the steaks from the fridge and leave out at room temperature for at least 20 minutes before cooking.
When ready to cook, place a medium sized cast iron skillet over high heat.
Dry the steaks very well with paper towels and season the steaks liberally with salt and pepper on all sides.
Once the cast iron is very hot, add 1 tablespoon of butter and avocado oil to the skillet and sear the steaks on the first side, until a deep crust is formed, about 3-4 minutes.
Once the first side is seared, turn the steaks over and continue searing until deeply caramelized. Sear the sides and fat cap as well.
Add a 2 more tablespoons of butter, the herb bundle and peeled garlic cloves and baste the butter onto the steak. Carefully tilt the pan towards you and push the steaks away from you in the pan. Then use a spoon to baste the butter onto the steaks, for another 30 seconds.
Once steaks are done, remove them to a cutting board and cover with foil to rest for at least 10 minutes.
Lower the heat in the cast iron and add a tablespoon of butter and the chopped garlic and saute for 30 seconds. Then add the mushrooms, season with salt and pepper and saute until mushrooms are tender, for 3-5 minutes.
Once steaks have rested, slice against the grain and serve with garlic mushrooms.