Step 1:Infuse the Milk

• In a medium saucepan, combine the milk, heavy cream, cinnamon stick, lemon peel, orange peel (if using), and vanilla bean seeds and pod (or vanilla extract).
• Heat over medium heat until the mixture is hot but not boiling.
• Once hot, remove from the heat and let the flavors infuse while it cools slightly.

Step 2:Prepare the Egg Mixture

• In a large mixing bowl, whisk together the egg yolks, sugar, and cornstarch until the mixture is smooth and pale.

Step 3:Temper the Eggs

• Gradually pour the warm milk mixture into the egg mixture, whisking constantly to prevent the eggs from curdling.
• If using a vanilla bean, remove the pod before mixing. Continue to whisk until fully combined.

Step 4:Cook the Custard

• Pour the mixture back into the saucepan and place over medium-low heat.
• Cook, stirring constantly with a wooden spoon or silicone spatula, until the custard thickens enough to coat the back of the spoon.
• This should take about 8-10 minutes. Do not let the mixture boil, as this can cause it to curdle.

Step 5:Strain and Chill

• Once thickened, remove the custard from the heat and strain it through a fine-mesh sieve into a large bowl to remove any lumps and the citrus peels. This step ensures a smooth custard.
• Pour the strained custard into individual ramekins or shallow dishes. Allow to cool to room temperature, then cover and refrigerate for at least 2 hours, or until well chilled and set.

Step 6:Serve

• Just before serving, sprinkle an even layer of granulated sugar (about 1-2 teaspoons) over each custard. Use a kitchen torch to caramelize the sugar until it forms a crisp, golden-brown crust. Alternatively, you can use the broiler setting on your oven: place the ramekins under the broiler for a few minutes, watching closely to prevent burning.
• Let the caramelized sugar cool and harden for a minute or two, then serve immediately. Crema Catalana is best enjoyed shortly after caramelizing the sugar to maintain the contrast between the creamy custard and the crunchy topping.