To start the cooking process, add the mushrooms to a dry nonstick skillet or well-seasoned cast-iron pan over medium-high heat. Don’t worry about sticking, just let the mushrooms sit on the bottom of the pan until they start to release their moisture. As the mushrooms cook, more and more moisture will escape into the pan. Continue to cook, pushing the mushrooms around the pan with a spatula from time to time to make sure they are all exposed to heat. After a few minutes, moisture will no longer escape from the mushrooms. Continue to cook until all of the water in the pan has evaporated and the mushrooms once again rest on a dry bottom. Add the butter to the skillet and stir the mushrooms in the pan. At this point, add the sliced garlic, if desired. Continue to sauté the mushrooms until they are golden brown and the edges are slightly crisp. Serve the mushrooms by themselves or as an element of another dish.