Preheat your oven to 250-275°C (480-530°F) with a pizza stone or baking tray inside if possible.
Slice the potatoes as thinly as possible using a mandoline or vegetable peeler.
Melt the butter in a hot frying pan and sauté the chanterelles for 4-5 minutes until lightly golden. Season with salt and freshly ground black pepper.
Spread the mascarpone evenly over both pizza bases. Top with the sliced potatoes, grated mozzarella and sautéed chanterelles, then sprinkle with the chopped rosemary.
Bake the pizzas one at a time for 5-7 minutes, or until the crust is crisp, the potatoes are tender and the cheese is melted and lightly golden.
Finish with a drizzle of extra virgin olive oil just before serving.