Begin by preparing a heavy bottomed saucepan. Pour in 3 1/2 cups of whole milk and add the cinnamon stick. Heat the milk over medium heat until it reaches a gentle simmer, stirring occasionally to prevent scorching. This step infuses the milk with the warm aroma of cinnamon, a hallmark of this dish. Remove the saucepan from heat and let it rest for 5 minutes to intensify the flavours.

In a medium bowl, whisk together the remaining 1/2 cup of milk and the cornstarch until smooth and lump free. This slurry will act as the thickening agent for the custard. Ensure there are no lumps, as they can compromise the final texture.

In a separate large bowl, whisk the egg yolks, sugar, and salt until the mixture is pale and slightly thickened. This ensures the sugar dissolves fully, creating a smooth base for the custard. Gradually add the corn starch slurry to the egg mixture, whisking continuously to combine.

Slowly pour the warm milk from the saucepan into the egg mixture, whisking constantly to temper the eggs. This step prevents the eggs from curdling. Once fully combined, strain the mixture back into the saucepan to remove the cinnamon stick and any small lumps.

Place the saucepan back on medium heat and cook the custard, stirring constantly with a wooden spoon or silicone spatula. Pay close attention to the bottom and sides of the pan to avoid sticking. Continue cooking until the custard thickens and coats the back of a spoon, about 5–7 minutes.

Remove the saucepan from heat and stir in the vanilla extract. This step enhances the flavour profile of the custard. Taste and adjust sweetness if necessary, adding a bit more sugar if desired. Let the custard cool slightly before transferring to serving dishes.

Divide the custard evenly among four serving bowls or ramekins. Allow them to cool to room temperature, then refrigerate for at least 2 hours to fully set. For a smoother surface, cover each bowl with plastic wrap, pressing it directly onto the custard to prevent a skin from forming.

To serve, sprinkle a light dusting of ground cinnamon over each bowl of custard. For an authentic touch, accompany the Leche Poleada with a side of Salvadoran sweet bread or a sprinkle of crushed graham crackers. Serve chilled, savouring the rich and creamy texture alongside the warm notes of cinnamon and vanilla.