In a medium saucepan, combine milk, cream, vanilla bean pod and seeds (or vanilla extract with a bit later), and salt. Heat over medium until just simmering; remove from heat and let infuse for 10 minutes.

In a separate bowl, whisk together egg yolks and sugar until pale and slightly thickened.

Slowly whisk the warm milk mixture into the yolks in a steady stream (tempering), stirring constantly.

Pour back into saucepan and cook over low heat, stirring continuously with a wooden spoon or silicone spatula, scraping the bottom, until the custard thickens enough to coat the back of the spoon (about 170–175 °F / 77–80 °C), about 5–8 minutes. Do not let it boil.

Strain the custard through a fine-mesh sieve into a clean bowl to remove the vanilla pod and any curdled bits.

If using vanilla extract, stir it in now.

Allow to cool; cover surface with plastic wrap to prevent skin forming, and refrigerate until well chilled.

Once chilled, gently whisk before serving. Use to top desserts like bread pudding, chocolate cake, fruit compote, or pour over berries.