STEP 1
In a small saucepan, combine 1 cup of granulated sugar, water, the cinnamon stick (or cinnamon powder), and lemon peel.
Bring to a boil, stirring until the sugar is dissolved. Reduce the heat and simmer for about 2-3 minutes. Set aside to cool.
STEP 2
In another saucepan, mix the whole milk, heavy cream, and orange peel. Heat over medium until hot but not boiling. Remove the orange peel and stir in the vanilla extract.
In a bowl, whisk together the egg yolks, 1/3 cup of granulated sugar, and cornstarch until smooth.
Gradually whisk in the hot milk mixture into the egg yolk mixture to temper the eggs.
STEP 3
Return the mixture to the saucepan and cook over low heat, stirring constantly, until the mixture thickens slightly (it should coat the back of a spoon but will still be pourable).
Strain the custard through a fine sieve into a bowl to remove any lumps. Gradually whisk in the cooled sugar syrup. Let the custard cool to room temperature, then cover and refrigerate until cold.
STEP 4
Roll out the puff pastry on a lightly floured surface into a rectangle about 1/4 inch thick. Roll the pastry tightly from the longer edge into a log.
Cut the log into 1-inch pieces. Place each piece into a muffin tin slot and press down to form a cup shape, ensuring the dough comes up to the edges. Try to make the pastry as thin as possible for the crispiest result.
STEP 5
Preheat the air fryer to 430°F (215°C).
Spoon the custard into the pastry shells, filling them about 3/4 full.
Bake in the air fryer for about 18 minutes, or until the pastry is golden and crisp, and the custard has puffed up with some characteristic black or brown spots on the surface. If your air fryer has a smaller capacity, you may need to bake them in batches.