Preheat the oven to 400°F.

Drizzle the potatoes with olive oil and season with the thyme, salt, and black pepper. Toss with a rubber spatula to coat.

Roast the potatoes on middle rack of oven for 25 minutes. At the 20 minute mark, begin searing the steaks.

Set a large skillet over high heat and add the oil and butter. Once the oil is very hot and shimmering, add the steaks. Sear steaks for 1 minute without moving. Flip and sear the other side for 45 seconds longer, then remove from heat.

Open the oven door and transfer the seared steaks from the skillet to the center of the baking sheet, pushing the potatoes to the edges of the sheet with a rubber spatula. Keep the drippings in the skillet and set aside. Roast the steaks and potatoes on middle rack of oven until potatoes are browned and crisp and steaks reach desired level of doneness, 9-12 minutes. Allow the meat to reach an internal temperature of at least 130°F for a medium steak. While the steaks roast, saute the mushrooms.

Check to see that steaks are done. Remove from oven or add time as needed.

Set the skillet over medium-high heat and add the mushrooms. Saute, stirring frequently, until they are shrunken and golden brown, 6-7 minutes. Add the minced garlic and saute until fragrant, about 30 seconds. Remove the skillet from the heat.

Top the steaks with the sauteed mushrooms. Allow to rest for 5 minutes before serving. Sprinkle with additional salt if desired.