Divide the principle bread dough into 8 equal balls, then transfer onto a flour-dusted tray and dust with flour. Leave to prove for 1 hour, or until doubled in size. Use a fish slice or pallet knife to separate the dough balls, then dust each ball with flour and place on a large flat surface. Use your fingers to gently press one ball of dough out into a fat round disc on a flour-dusted surface, picking it up and gently turning to stretch it to 30cm in diameter, using gravity to help you. Stretch it over the back of your fists, then place on a flour-dusted surface – the dough should be a little thicker around the edges. Pull it into shape and give it a jiggle so you know it’s free-moving. Repeat with the remaining dough balls – at this point you can either scale up the topping quantities, depending on the number of pizzas you want to cook, or freeze the remaining bases ready for cooking another day. When you’re ready to cook, preheat the oven to 240°C/475°F/gas 9 (or preheat your pizza oven, if using). Rub 1 tablespoon of extra virgin olive oil over a pizza base, then tear over the mozzarella. Toss the grapes with ½ a teaspoon of vinegar, a splash of extra virgin olive oil and a handful of blanched hazelnuts. Strip over the rosemary leaves and scrunch together with your hands, breaking up the nuts as you go. Finely grate over the Parmesan, then scatter the toppings over the base. Bake for 7 to 10 minutes, or until golden and crispy (or around 4 minutes if using a pizza oven – please note that pizza ovens can vary).