Preheat oven and a lightly greased roasting pan 220°C fan forced. Scatter mushrooms over the base of hot pan. Combine the oil, vinegar and salt and pepper in a jug then pour over the mushrooms and turn to coat. Roast mushrooms for 5-7 minutes until light golden.
Spread the pizza bases evenly with passatta sauce. Top with prosciutto, roasted mushrooms, olives then crumble over the feta.
Place pizzas onto baking trays and bake 10-12 minutes, swapping the trays over in the oven until bases are crisp. Combine the basil and fresh tomato and spoon over the pizza. Season with salt and pepper and serve.