Prepare the Custard Base: Heat the cream, milk, and half the sugar in a saucepan until steaming. Add vanilla beans, cinnamon sticks, or chocolate if using.
Whisk the Yolks: In a bowl, whisk egg yolks, remaining sugar, salt, and cornstarch until pale yellow.
Temper the Eggs: Gradually add hot cream to the egg mixture, whisking to prevent curdling. Return to the saucepan and cook until thickened.
Strain and Cool: Strain through a sieve, discard solids, and cool in an ice bath.
Chill: Cover and refrigerate for at least 4 hours.
Churn and Freeze: Pour into an ice cream maker and churn as per manufacturer instructions. Freeze for 4 hours.
Notes
For Mango Chile, add 1 cup of mango puree and ¼ teaspoon of ground chile de árbol.
For Horchata flavor, infuse the cream with ½ cup rice and 1 cinnamon stick for an hour.
To make it softer, add a tablespoon of mezcal or tequila.