Combine all the ingredients and mix together in a bowl. Set aside. This should serve up to 8 portobello mushroom pizzas.
Olive Oil Herb Spread
Combine the herbs with the olive oil and stir. Brush on both sides of the portobello mushroom. This mix is enough to make 4 portobello mushroom pizzas.
Grill the Portobello Mushroom Pizza
Scrape the fins from the underside of the mushroom using a tablespoon
Brush both sides of the mushroom with the olive oil herb spread
Grill the mushroom upside down (with the cap facing up) for three to five minutes
Remove the mushrooms from the grill and turn them over
Add tomato sauce, cheese and other toppings
Place on the grill until the cheese is fully melted (about five minutes)