Position 1 oven rack in the center and the second rack on the bottom of the oven and preheat to 450 degrees F. Roll out each piece of pizza dough into a 13 1/2 by 8 1/2-inch rectangle. Transfer to separate large baking sheets.
Spoon the marinara sauce over the pizzas, dividing equally and leaving a 1-inch border around each pizza. Sprinkle the mozzarella and Fontina cheeses over the pizzas, dividing equally. Sprinkle the mushrooms and pancetta over the cheese. Bake the pizzas until the crusts are crisp and brown on the bottom and the cheese is melted on top, about 15 minutes. Cut the pizzas crosswise into rectangular slices and serve immediately.
Mix the warm water and yeast in a small bowl to blend. Let stand until the yeast dissolves, about 5 minutes. Mix the flour and salt in a food processor to blend. Blend in the oil. With the machine running, add the yeast mixture and blend just until the dough forms. Turn the dough out onto lightly floured surface and knead until smooth, about 1 minute. Transfer the dough to a large oiled bowl and turn the dough to coat with the oil. Cover the bowl with plastic wrap and set aside in a warm draft-free area until the dough doubles in volume, about 1 hour. Punch the down dough and form into ball. The dough can be used immediately or stored airtight in the refrigerator for 1 day.