Drain the tomatoes, keeping the juice in a bowl. Remove and discard the seeds and any liquid in the tomatoes (see note). With your hands, coarsely crush the tomatoes. Place the crushed tomatoes in the bowl of reserved juice and combine with the remaining ingredients. Season with salt and pepper. Set aside.
Place a pizza stone or inverted baking sheet on the middle rack of the oven. Preheat the oven to 450°F (230°C).
In a skillet, brown the mushrooms in the oil. Season with salt and pepper. Set aside.
Divide the dough in half. On a floured work surface, stretch or roll out one piece of dough at a time into a 14-inch (35-cm) disc, leaving a thick border. Place on a piece of parchment paper. Spread 1 cup (250 ml) of the tomato sauce over the entire surface. Sprinkle with half of the grated mozzarella. Top with the meat of one sausage and half of the mushrooms. Bake for 12 minutes. Top with half of the fresh mozzarella. Continue cooking for 5 minutes or until the crust is golden brown and the cheese has melted. Repeat with the remaining ingredients for a second pizza.
If you seed the tomatoes, you'll have a much smoother sauce. By removing any liquid inside the tomatoes, you will also get a thicker sauce.