For The Pizza Base For The Topping

1. Raise the temperature of the oven to 425°F (220°C) or gas mark 7. Insert a pizza stone or a large baking tray into the oven to heat up.
2. Heat the milk in a small saucepan over low heat until it is lukewarm, then pour 50ml into a jug with the sugar and yeast. Mix well, then set aside for a couple of minutes until it begins to bubble.
3. Meanwhile, sift the flour, xanthan gum, and salt into a large bowl, and make a well in the center. In a separate bowl, combine the egg, 3 tablespoons of olive oil, and the remaining milk, then pour it into the well, along with the yeast mixture. Gradually incorporate the ingredients with a fork until a smooth dough forms.
4. In a small cup, combine the bicarbonate of soda and vinegar, then swiftly knead it into the mixture. Place the dough in a lightly oiled bowl, cover it with a damp tea towel, and let it rise in a warm place for about an hour or until doubled in size.
5. Meanwhile, prepare the topping. Pick the basil leaves from the stalks and set aside, then finely chop the stalks. Peel and finely chop the garlic. In a large frying pan over medium heat, heat a drizzle of olive oil, then add the basil stalks and garlic. Cook for a few minutes or until golden brown. Add the tinned tomatoes and mash them with the back of a wooden spoon, then simmer for 5 to 10 minutes, or until thickened. Transfer to a blender with half of the reserved basil leaves, blend until smooth, and season with salt and pepper to taste.
6. Once the dough has doubled in size, divide it into four equal pieces on a floured surface. Roll out each piece to a diameter of roughly 30 cm and a thickness of 2 mm. Transfer the pizza bases to the preheated pizza stone or baking tray (you'll need to do this in batches), then spread the tomato sauce over the top, leaving a 2 cm gap around the edges. Tear the mozzarella into pieces and scatter it over the sauce, then bake in the hot oven for 10 to 12 minutes or until golden brown and crispy. Sprinkle the remaining basil leaves on top and serve.