Using a paring knife or a peeler, peel 3 strips of orange peel, making sure you don’t get any of the bitter white pith. Next, do the same with the lemon, and peel off 2 strips.
Put the milk, orange peel, lemon peel and cinnamon stick in a saucepan.
With a pairing knife, slit the vanilla bean lengthwise, keeping the ends uncut. Scrape some of the seeds out and add them to the saucepan together with the vanilla bean pod. Slowly, bring the mixture to a boil over low heat.
Remove from the heat and allow the mixture to cool for about 10 minutes.
In a medium bowl, whisk the egg yolks with the sugar and cornstarch until pale, thick and creamy.
Strain the milk through a sieve and discard the solids. Return the milk to the saucepan.
Whisking constantly, slowly add about a quarter of the infused milk into the egg yolk mixture. Make sure you whisk vigorously to prevent the eggs from cooking. Add about another quarter of the milk into the egg mixture while constantly whisking.
Now that the eggs are tempered, slowly stir in the egg mixture into the saucepan.
Cook over medium-low heat stirring frequently and cook until the mixture thickens and covers the back of a spoon, about 3-4 minutes.
Remove from the heat and pour the mixture into individual clay dishes or ramekins. Place them on a sheet pan and let them cool before refrigerating. Cover them with plastic wrap and refrigerate for 4 hours or preferably overnight.
Before creating the caramelized sugar topping, you can let the crema Catalana come to room temperature if preferred.
Sprinkle a thin layer of granulated sugar all over the top of the custard (about 1 tablespoon of sugar) and using a kitchen blow torch, caramelize the top. Serve with berries if desired.