Heat olive oil in a large skillet on medium heat until hot but not smoking. Add sliced mushrooms and garlic, and saute for about 3 minutes, regularly stirring with a spatula.
Sprinkle the mushrooms with a little bit of salt, cover with the lid and continue cooking the mushrooms for another 2 minutes, occasionally stirring. Having the lid on will allow mushrooms to generate some moisture and not get burned.
Remove the lid after mushrooms have released their moisture and saute for another 5 or so minutes on medium-high heat, stirring with a spatula.
Total cooking time from the beginning to the end should be under 15 minutes.
Season with salt and pepper, to taste. Sprinkle with chopped chives or green onions.