Combine the egg yolks, sugar, and cornstarch In a medium bowl, whisk together the egg yolks, sugar, and cornstarch until they form a smooth, pale yellow mixture. Slowly pour in one-third of the milk as you whisk, ensuring the cornstarch dissolves completely and there are no lumps.
Infuse the remaining milk with lemon and cinnamon In a saucepan, bring the remaining two-thirds of the milk to a gentle boil. Add the lemon peel (try to avoid the bitter white pith) and cinnamon stick to infuse the milk with a subtle citrus and spice aroma. Let it boil for about 3 minutes, keeping an eye on it to prevent overflow.
Remove aromatics After the milk has simmered with the lemon peel and cinnamon for several minutes, take the saucepan off the heat. Use tongs or a spoon to fish out and discard the lemon peel and cinnamon stick.
Incorporate the egg mixture Strain the egg yolk mixture into the hot milk, pouring slowly and whisking constantly as it streams into the pan. This straining step helps catch any potential lumps or bits of cooked egg, ensuring a silky custard texture.
Cook until thickened Return the saucepan to medium heat and continue stirring gently but continuously. Allow the mixture to come to a soft boil, keeping a close eye on it to prevent scorching. As soon as it starts to thicken—usually within a minute or two of boiling—take it off the heat.
Cool and set Divide the custard into individual serving bowls or ramekins. Let them cool at room temperature for a few minutes, then transfer to the refrigerator if you prefer a chilled dessert. The custard will continue to set as it cools.
Caramelize the top For a classic finishing touch, sprinkle a thin layer of sugar over each custard. Use a kitchen blowtorch to melt and caramelize the sugar until it forms a golden, glassy crust. If you don’t have a blowtorch, place the bowls under a preheated broiler for a minute or two, watching carefully to avoid burning. Serve warm or chilled with a crisp caramel top.
