Step 1: Prepare the Puff Pastry - Preheat your oven to 220°C (428°F). Roll out the puff pastry slightly and cut out circles larger than your custard cups.
Step 2: Grease the Cups - Grease your custard cups or muffin tin with a little oil and press the pastry circles into them.
Step 3: Make the Custard Filling - In a saucepan, combine sugar and water, stir over medium heat until dissolved, then boil for 5 minutes. Let cool. In a bowl, whisk egg yolks, flour, and milk, then gradually add the sugar syrup. Add cinnamon stick and lemon zest, then strain the mixture.
Step 4: Fill the Pastry Cups - Pour the custard mixture into each pastry cup, filling them about three-quarters full.
Step 5: Bake the Tarts - Bake in the preheated oven for approximately 15-20 minutes until golden with a few dark spots.
Step 6: Cool and Serve - Allow the tarts to cool in the tray for a few minutes, then transfer to a wire rack. Dust with cinnamon or powdered sugar before serving.
