In a small bowl, mix the butter, herbs, garlic, and salt with a spatula until combined. A handheld mixer with beater attachments can also be used.
Transfer the butter onto a piece of parchment paper. Roll and form the butter into a log about 2 inches in diameter using the parchment paper. Transfer to the refrigerator to chill for at least 2 hours or until ready to use. This can be made in advance.
When the butter is chilled and firm enough to handle, slice into 1/4 inch thick rounds.
You only need 1-2 rounds per steak; you will have extra compound butter, that can be used for other recipes. Try it in a baked potato, with seafood, and more!
Make the Steak
Bring the steak to room temperature; this usually takes 20-30 minutes after removing it from the refrigerator. Pat the steaks on both sides with a paper towel to remove excess moisture.
Season both sides of the steak generously with salt and pepper. You can also use your favorite steak rub if you wish.
Heat a heavy skillet (ideally a cast-iron skillet) over high heat. Add the oil, and swirl to evenly coat the skillet.
Add the steak and lower the heat to medium-high heat. Cook for 4 minutes per side, until browned on both sides. Use tongs to turn the steak onto its side and sear the fat cap.
Lower the heat to medium-low heat and drop in 1 round of the compound butter, the rosemary, and the smashed garlic. Use a spoon to scoop the fragrant, melted butter over the steak. When the garlic is browned, and the steak is cooked to your liking (135°F for medium-rare; see temperature chart in notes), transfer to a cutting board to rest for 7 to 8 minutes.
Carve the steak away from the bone and slice against the grain. Serve with an additional round of compound butter if you wish (optional).
Notes
Certified Angus Beef® Steak Recipe Notes/FAQs
Is T-bone the same as Porterhouse steak? Visit any butcher or steakhouse, and you will see these terms used interchangeably. Both T-bone and Porterhouse steaks have both the strip loin and tenderloin filet, however, Porterhouse steaks are cut from the rear of the short loin and have a wider tenderloin filet. T-bone steaks are cut closer to the front of the short loin and have a thinner tenderloin filet.
What kind of pan should I use for cooking my steak? I recommend using a heavy, good quality skillet that conducts heat efficiently. I prefer using a cast-iron skillet, such as the Staub Cast Iron Fry Pan I used in this post.
How do I know my steak is done? Since various factors (steak thickness, temperature, etc.) can impact cook time, I recommend using a meat thermometer. I have the ThermoWorks Classic Thermapen. See below for the internal steak temperatures: