If needed, clean the mushrooms by filling a bowl with water and submerging the mushrooms. Agitate them quickly to remove any stuck dirt bits. Let the mushrooms rise to the top and the dirt bits settle to the bottom of the bowl and remove the mushroom. Squeeze the remaining moisture out and then slice them to an approximately uniform thickness.
Heat a very large skillet over medium-high heat until hot at which point add the butter or vegetable oil. Add the mushrooms and shake the skillet to coat. Add the garlic glove and other desired herbs if you would like. Other herb ideas include rosemary, sage, and thyme.
Cook over medium-high heat and shake the skillet frequently. At first, the mushrooms will seem dry and will absorb the fat. Continue to shake the skillet until the mushrooms begin to color and release their juice, 3-4 minutes.
Meanwhile, slice the baguette or other bread into desired sizes and toast.
Spread goat cheese over crostini in a thin layer, ideally completely flat or with a slightly rounded center. Using a small spoon, scoop mushrooms onto each piece of toast. Sprinkle with parsley.