Heat a large oven-proof skillet over medium-high heat. Add the olive oil and heat until shimmering.
Sear the beef tenderloin on all sides until browned, about 3-4 minutes per side.
Transfer skillet to the oven and roast for 15-20 minutes, or until an instant-read thermometer registers 125°F for medium-rare.
Remove the skillet from the oven and let the beef rest for 10 minutes.
Meanwhile, add the butter to the same skillet and heat over medium heat until the butter has melted and begun to brown. Stir in the shiitake mushrooms and ginger and cook for 3-4 minutes, or until the mushrooms are softened.
Slice the beef and serve with the mushrooms and brown butter. Sprinkle with freshly chopped parsley.
Interesting Facts
Beef tenderloin is a lean, tender cut of beef that is often served as a steak.
Shiitake mushrooms are a type of mushroom that has a meaty texture and a rich, earthy flavor.
Brown butter is butter that has been cooked until it turns a golden brown color and has a nutty, toasted flavor.