Pat your steaks dry and let them sit at room temperature for 20 minutes or so as you slice the mushrooms and heat the pan. Sprinkle them with salt.
Set a large, heavy skillet over medium-high heat (cast iron is ideal), and add a drizzle of oil, turning it to coat the bottom of the pan.
Cook for about 5 minutes, until the bottom is deep golden and crusty, then flip and cook for another 4-5 minutes for medium-rare, or until done to your liking. flipping and basting with butter (tip the pan occasionally to help it pool) until cooked to your liking. Set aside to rest.
If you like, add a couple tablespoons of butter to the pan and cook the mushrooms, scraping up any flavourful browned bits in the bottom of the skillet, until the mushrooms are soft and starting to turn golden.
Sprinkle with the leaves pulled off a sprig of thyme, or a bit of chopped fresh rosemary, if you like.
Serve the mushrooms over the steak.