Make up the dough following the pack instructions. Roll out thinly to make a rectangle about 30 x 40cm, then transfer to a well oiled baking sheet. Cover with cling film and leave to rise for 20 mins. Preheat the oven to 220C/fan 200C/gas 7.
Slice the potatoes thinly and boil in salted water, or steam, until just tender, about 3-4 mins, then drain well and pat dry. Shred the spring onions. Thinly slice the cheese.
Spread the potatoes over the pizza dough and drizzle with a little olive oil. Scatter over the onions, cheese and lardons. Bake for 15-20 mins, until the topping is crisp and golden. Cut into squares to serve.