In a large mixing bowl, combine all the ingredients and knead until smooth and elastic. The dough will be slightly sticky. Add a little more flour as needed.
Cover with plastic wrap and leave to sit for 30 minutes.
After 30 minutes, knead the dough again, cover, and leave to proof for 2 hours in a warm spot.
Make the caramelized onions:
To the caramelized onion jam, add ½ teaspoon 5-spice powder and mix.
Make the garlic oil paste:
In a food processor, add in the garlic and pulse until fine. Drizzle in the oil and continue to pulse until a smooth paste forms.
Transfer garlic oil paste into a clean jar and store in the fridge for up to 2 weeks.
Assemble:
Place the Baking Steel on the bottom rack of your oven.
Preheat the oven to 500°F/260°C. (Do this about 1 hour before you plan to bake the pizzas off).
Dust your work surface with some flour. Divide the pizza dough into 3 portions.
Lay a piece of parchment paper and stretch out the pizza dough into a circle about 10-12" in diameter, leaving a perimeter for the crust.
Spread 1 tablespoon garlic oil paste on the surface of the dough. Add the roast bbq duck slices, caramelized onions and green onions.
Use a pizza paddle and place the pizza dough onto the Baking Steel and cook for 6-7 minutes, until golden brown. You can use the broiler for 2-3 minutes if you prefer a darker crust.
Remove from oven. Garnish with extra green onions, cilantro, and red onions. Drizzle hoisin sauce on top.
Slice the Peking Duck pizza and serve immediately. Repeat with the remaining pizzas.