Heat the Base:
In a medium saucepan over medium heat, combine the heavy cream, milk, half of the sugar, and salt. If using a vanilla bean, add it now with seeds scraped in. Heat until steaming (do not boil).
Whisk the Egg Yolks:
In a separate bowl, whisk the egg yolks with the remaining sugar until pale and creamy.
Temper the Yolks:
Slowly pour about ½ cup of the hot cream mixture into the egg yolks while whisking constantly. This prevents curdling.
Combine and Thicken:
Pour the tempered yolks back into the saucepan. Cook over low heat, stirring constantly with a wooden spoon, until the custard thickens enough to coat the back of the spoon (170–175°F / 77–80°C).
Strain and Chill:
Remove from heat and strain through a fine-mesh sieve into a clean bowl to remove any cooked egg bits. Stir in vanilla extract if not using a bean. Cover and chill for at least 4 hours or overnight.
Churn the Ice Cream:
Pour the chilled custard into your ice cream maker and churn according to the manufacturer’s instructions (usually 20–25 minutes).
Freeze to Firm:
Transfer to a lidded freezer container and freeze for at least 2 hours before serving for a firmer texture.