Make the dough. Mix the flour, yeast, oil and salt together in a large bowl. Mix together the sugar and warm water then make a well in the centre of the dry ingredients. Pour the sugar and water into the well. Gradually mix the wet and dry ingredients together and then turn out onto a floured work surface. Knead for 10 minutes. Flour the outside of the ball of dough then place in an oiled bowl. At this stage you can either prove for about 15 minutes somewhere warm or put it into the fridge until you're ready to use.
Preheat the oven to 200°C. Make the sauce. Heat the olive oil over a medium heat. Add the onion, garlic, plenty of salt and 40ml of water. Once the water has evaporated pour in the tin of tomatoes and cook down until it's almost dry. Mix in the tomato puree and oregano and leave to cook a little more until it has a thick consistency. Tip out onto a plate and allow to cool.
Make the pesto. Place the basil, pine nuts and pecorino in a blender and blend with a drizzle of olive oil. Keep adding olive oil until you reach a consistency thin enough to drizzle over the pizzas.
Make the pizzas. Split the dough into 16 balls and roll each one into a circle. Top half with a spoonful of sauce then split the chicken, half the mozzarella and cheddar between them. Top the other half of the pizza bases with a spoonful of sauce followed by a drizzle of pesto and the rest of the mozzarella. You'll probably need to do all this in batches unless you have a crazy amount of baking trays! Bake the pizzas for 10-12 minutes.