Trim the bottom of the stem off of the mushrooms, and cut the larger mushrooms (the white button and the trumpet royal) into thick slices parallel to the stem. Remove the bottom part of the stem of the funny-shaped mushrooms (the maitake and the black trumpet) and cut into large pieces. Save the scraps to make mushroom sauce to finish the pizza with!
To make the mushroom sauce, boil 1 cup chicken stock and 1 cup water with the mushroom scraps. Reduce the sauce down until the mushroom flavor is pronounced. Strain out the shrooms and it's ready to use.