Heat a large cast iron or non-stick skillet over medium-high heat. Season steak with Ultimate Steak Seasoning; set aside.
When hot add oil and butter to skillet. Carefully add steak to skillet. Sear 3-4 minutes. Turn steak over.
Using a spoon, frequently ladle butter oil in skillet over steak as it continues to sear until desired doneness is reached on an instant-read food thermometer (145°F for medium-rare, 160°F for medium) about 4-8 minutes. Remove steak from skillet; let rest 5-10 minutes.
Add mushrooms and Rustic Herb Seasoning to hot skillet; reduce heat slightly. Sauté until golden brown, about 5-6 minutes. Serve steak with sautéed mushrooms.