In a saucepan, combine milk, cinnamon stick, and lemon zest. Heat until just simmering, then remove from heat and let steep for 10 minutes.
Prepare the Egg Mixture:
In a bowl, whisk together egg yolks, 1/2 cup sugar, cornstarch, and vanilla extract until smooth.
Temper the Eggs:
Gradually pour the warm milk into the egg mixture, whisking constantly to avoid curdling.
Cook the Custard:
Return the mixture to the saucepan and cook over low-medium heat, stirring constantly, until thickened and coating the back of a spoon (about 5–7 minutes).
Strain and Cool:
Remove the cinnamon stick and lemon zest. Strain the custard through a fine mesh sieve into individual ramekins. Let cool to room temperature, then refrigerate for at least 2 hours.
Caramelize the Top:
Sprinkle 1–2 teaspoons of sugar evenly over each custard. Use a kitchen torch to caramelize until golden and crispy. If you don’t have a torch, place under a broiler for 1–2 minutes, watching closely.
Serve:
Let the caramelized sugar set for a minute, then serve immediately for the perfect contrast of creamy custard and crisp topping.
