For the dough: Place the milk, water and yeast in a mixing bowl, then warm for 2 min/37°C/speed 1. Add the flour, oil, egg, garlic powder and salt, then knead the dough for 5 minutes. Meanwhile, grease a large bowl. Transfer to a prepared bowl, and cover with greased cling film and leave to rest until doubled in size (approx. 1 hour). Meanwhile, clean the mixing bowl and make the pesto.
For the pesto: Place the mozzarella in a mixing bowl and grate for 3 sec/speed 8. Transfer to a bowl and set aside. Place the pecorino in a mixing bowl and grate for 15 sec/speed 10. Add the pine nuts, basil, oil, garlic and salt then chop 20 sec/speed 7. Transfer to a bowl and set aside.
To assemble: On a lightly-floured surface, divide the rested dough into 4 equal-sized pieces and shape into balls. Take 1 ball and cover the remainder with greased cling film. Place the dough ball on a large sheet of baking paper then roll out to a disc (diameter 25cm). Transfer to a 28cm baking tray and brush the border with egg wash.
Spread the passata over dough, leaving a 2cm border. Sprinkle over the garlic powder, oregano and pepper.
Roll out a second ball of dough to make a 25cm disc, then place on top of the first disc and brush the border with egg wash. Spread over the reserved pesto, leaving a 2cm border.
Roll out a third ball of dough into 25cm a disc and place on top of the second disc and brush the border with egg wash. Scatter over the reserved grated mozzarella, leaving a 2cm border. Roll out the last ball of dough to a 25cm disc and place it on top.
Gently press a 5cm cookie cutter into the centre of dough, without breaking through, then remove. Using a sharp knife, cut all the dough layers into 16 equal-sized slices, from the marking of the cutter in the centre to the edge.
Take two adjacent strips of dough, one in each hand, and twist them away from each other twice, so the top side is facing up again. Repeat with the remaining strips of dough, all the way around, then pinch the ends of the adjacent strips together all around the bread to create eight star-like points.
Cover with greased cling film and leave to prove in a warm place for approx. 45 minutes. Towards the end of this time, preheat the oven to 200°C.
Brush all over with the egg wash. Bake for 15-17 minutes until golden brown on top.
Leave on a tray to cool for 5 minutes and serve warm, for everyone to tear off pieces at the table.