Clean mushrooms, if needed, by quickly rinsing under cold water, then patting dry.

Place a large skillet over high heat and add the oil. Let oil heat for 2 minutes, then add the mushrooms. Let cook, untouched, for 3 minutes.

Stir mushrooms every 3 minutes for ~9 minutes total, until mushrooms start to brown. Add in butter and salt, and cook for another 2 minutes until butter is absorbed. Serve immediately.