In a saucepan, heat the milk (reserve 1 cup) with the cinnamon stick and lemon peel to infuse the flavors. In a separate bowl, whisk the egg yolks with the sweetener.

Mix the reserved 1 cup of cold milk with the cornstarch until smooth. Add the cornstarch mixture to the egg yolks, then gradually pour in the warm infused milk while stirring constantly. Once combined, return the mixture to the heat and cook, stirring continuously, until it thickens to your desired consistency.

Pour the custard into individual ramekins and let cool. Sprinkle the tops with brown sugar and caramelize using a kitchen torch or traditional caramelizing iron. Serve.