Cut the mushroom into 1/2 inch steaks or as best you can, uniformly.
Place them in a dry pan on medium. Cook for 5 to 7 minutes and flip. When the mushrooms have released water and start to brown, add the butter. Make sure every piece gets a bit on both sides. Be delicate as you handle them and don't stir them around. Season with salt and generous amounts of fresh ground pepper. Bring the heat down to low and cook until both sides are golden brown.
The furry fronds will go from soft to crispy and soak up all that butter. MMMMPH. So satisfying as a side dish or garnish to a warm salad.