I am not including any nutritional info for this because there are so many different options for topping a pizza, not to mention, the different sizes of the mushrooms available.
What I did for this picture is cut off the stem of the portobello mushroom, scrape the dark gills out of the inside.
Top with a little pizza sauce.
I added crumbled sausage right on top of the sauce, then covered with mozzarella cheese and topped with pepperoni.
Bake at 400 degree oven for anywhere from 15-25 minutes depending on the size of the mushroom and the amount of toppings.
I also like to broil the top for just a minute to get that slightly browned cheese.