1/3cupcaster sugar(increase it to 1/2 cup if you prefer a sweeter custard); to make your own caster sugar pulse granulated sugar in a blender until very fine
1/8teaspoonkosher or sea salt
2teaspoonscornstarch (optional)(if you prefer a thicker consistency)
1cupheavy cream
1cupwhole milk
1vanilla bean, split lengthwise, seeds scraped out (add both the seeds and pod to the saucepan)
In a medium-sized bowl, whisk together the egg yolks, sugar, salt and cornstarch (if using) until the mixture is smooth.Heat the milk, cream and vanilla in a small saucepan just until bubbles form along the edges of the pan. If you're using a vanilla bean pod, turn the heat off and let it steep for 20 minutes. Then re-heat it until bubbles form along the edges. If you're using vanilla bean paste, there's no steeping necessary, simply proceed. Remove 1/2 cup of the hot cream and whisk it into the egg mixture, whisking constantly. Gradually pour the egg yolk mixture back into the saucepan with the rest of the cream mixture, whisking constantly to prevent clumping. Continue to cook, whisking constantly, until the mixture leaves a path on the back of spoon when you draw your finger across it. DO NOT BOIL. For accuracy I recommend using an instant read thermometer; the temperature should read 170-175 F (77-79 C).For a smoother texture, pour the custard through a fine mesh sieve. The custard can be used immediately and served warm. Otherwise, let the custard cool and refrigerate, pressing plastic wrap down onto the surface to prevent a skin from forming. It will keep in the fridge for up to 3 days.
Notes
Adjust the thickness of the sauce to serve your purpose by adding more or less cornstarch.