You can make the pizza dough up to 48 hrs before you want to cook the pizza. Warm the milk in a saucepan until steaming but not boiling. In a large bowl combine the flour, yeast, sugar and 1 tsp salt. Add 1/2 tbsp oil to the milk and leave to cool until just warm –when you place a finger in the liquid it should feel body temperature. Pour the liquid into the bowl and either mix with a wooden spoon or food mixer, until the ingredients are well combined. Tip out onto your work surface and knead for 10 mins, or continue mixing in the mixer for 5-7 mins, until you have a smooth and elastic dough. Clean and oil the bowl, return the dough and cover with cling film. Leave somewhere warm to rise for 1-2 hrs, until doubled in size, or place in the fridge for up to 48 hrs.
Meanwhile, make the sauce. Pour the remaining oil and passata into a saucepan and add the squashed garlic, oregano and a pinch of sugar. Season well and simmer for 5-10 mins, until the sauce is thick. Remove the garlic cloves and set aside until you’re ready to assemble the pizza.
If the dough has been chilled remove from the fridge and leave at room temperature for 1 hr. Dust the work surface with polenta and tip the dough onto it. Punch the dough down to knock out the air bubbles then shape into a disk. Roll out the dough to a pizza base, about 35cm wide. Dust a large baking sheet with polenta and place the dough on top, making sure the dough can move around freely. Use 125g of the mozzarella to create a ring around the outside edge of the pizza base, leaving 1/2cm gap between the edge. Brush a little water inside the mozzarella ring then fold over the outside edge to enclose the mozzarella and create a stuffed crust. Press firmly to stick the dough in place.
Spoon the sauce over the middle of the base and top with the remaining mozzarella. Scatter with your chosen toppings (save any fresh herbs for scattering over at the end) and brush the stuffed crust with a little oil, then lightly cover with oiled cling film and set aside for 20-30 mins, until the dough has puffed up a little. Meanwhile heat oven to 240C/220C fan/gas 9 with a large baking sheet on the middle shelf to heat up.
When the oven is hot and the pizza dough has puffed up, quickly open the oven door and slide the pizza onto the hot tray. Shut the door and cook for 15-20 mins, or until bubbling and cooked through. Leave to cool for a few mins before eating.