Preheat the oven to 220°C, 425°F, Gas 7. Stretch the dough into a rectangle as in our recipe. Spread the tomato sauce evenly over the base, leaving a 1cm/½in gap around the edge. Scatter over the cubed mozzarella. Break the Nduja sausage into small pieces and scatter evenly over the base then scatter the roquito peppers, green chillies and peppers on top. Sprinkle over half of the Grana Padano cheese and add the slices of Calabrese sausage. Season with the oregano, transfer to a non-stick baking tray and cook in the preheated oven for 10-12 minutes.
While the pizza is cooking, mix the pesto and watercress gently in a bowl. Remove the pizza from the oven. Tear the fior di latte mozzarella into pieces and scatter over. Scatter over the pesto and watercress mix and finish with a sprinkle of the remaining Grana Padano. Serve straight away.