For the pizza dough:

1. In the bowl of a stand mixer (or a large metal bowl) stir all ingredients together until well combined. If using a stand mixer fit it with the hook attachment and mix on low for 4 minutes. The flour should form a coarse ball. Let the dough rest for 5 minutes , then mix on medium for 2 more minutes, or until the dough clears the sides of the bowl and sticks just a little to the bottom. If the dough is too soft and sticky mix in some flour, if it is too stiff add some more water.
2. Transfer the dough to a floured surface, dust the top with flour and working from four corners fold the dough into a ball. Place in a bowl, that has been brushed with olive oil and cover with plastic wrap. Let it sit at room temperature for 1 hour, to double its size. Then punch a hole in the dough, reshape, place in a bowl and refrigerate for at least 2 hours. Remove dough from the fridge 2 hours before using. Divide dough into 6 parts. Form 6 balls and brush them with olive oil.

To cook pizza on a gas grill, using an pizza stone:

1. Place a pizza stone on your grill. Close the cover. Preheat a gas grill to 425-450 F.
2. Once the grill has heated, assemble the pizzas. Depending on the size of your pizzas and stone, you may need to grill them one by one or two at a time.
3. Generously sprinkle a pizza peel with polenta.
4. Spread pizza dough over pizza peel. Add crushed tomatoes, leaving at least 1/2 inch around the edges. Top with mozzarella cheese.
5. Carefully transfer pizza to heated pizza stone. (You may need to use a spatula to help yourself.)
6. Grill pizza for 10-12 minutes, to the desired doneness. Outer edges should be brown, all around the crust.
7. Using a metal spatula, carefully loosen pizza, if it is stuck to the stone. With a pizza peel remove pizza and transfer to a cutting board.
8. Season arugula with roasted garlic olive oil, white balsamic vinegar, salt and pepper. Top pizza with prosciutto, Parmesan and seasoned arugula. Cut and serve.