Make the Pastry: Pulse flour and salt together, then add butter until it resembles wet sand. Add ice cold water until clumpy.
Chill the Pastry: Shape into a disc, wrap in cling film, and refrigerate.
Roll Out the Pastry: Roll out the chilled pastry between parchment paper to fit a 9-inch tart pan.
Blind Bake the Crust: Fill with baking beans and bake at 200°C for 20 minutes, then remove beans and bake for another 3 minutes.
Prepare the Filling: Heat garlic oil, add chilli flakes, then sauté leeks until softened. Add mushrooms and cook until water evaporates.
Add Chicken: Mix in shredded chicken with the mushroom mixture.
Prepare Custard: Whisk together cream, eggs, salt, pepper, and chilli flakes.
Assemble the Quiche: Layer the mushroom and chicken mixture in the crust, sprinkle with Parmesan, and pour custard over.
Bake the Quiche: Bake at 180°C for 20-25 minutes until custard is set.