Clean your mushrooms.

Slice mushrooms. 

Add sliced mushrooms and water to a pan at medium-high heat.

Allow the mushrooms to steam until the water and juices have evaporated.

Spread mushrooms around in the pan so that all of the mushrooms are laying flat.

Add olive oil and stir mushrooms until they absorb the oil.

Add butter and stir mushrooms until they have absorbed some butter.

Mushrooms are done when they appear lightly browned and soft.