- Set a strainer over a medium bowl, and place the bowl in larger bowl filled with ice.
- Pour 1 1/2 cups of the half & half into a medium saucepan. Add the slit vanilla bean, sugar, and salt. Bring the mixture to a simmer over medium heat, stirring until the sugar dissolves.
- In a medium heatproof bowl, whisk together the egg yolks and remaining half & half. Ladle half of the hot liquid from the pan into the yolk mixture, whisking constantly.
- Return the yolk mixture to the saucepan, whisking constantly. Return to a very low simmer, watching carefully. Don't let the custard boil; if it does, the yolks will curdle and the custard will be lumpy.
- To test the custard, dip a spoon into it and run your finger across the back of the spoon. When the custard is thick enough to leave a clean mark from your finger, take it off the heat and immediately pour it through the waiting strainer into the bowl over the ice bath to stop the cooking. Scrape the pulp from inside the vanilla bean and add it to the strained custard. If using vanilla bean paste instead, stir it in now.
- Once the custard is cool, cover and refrigerate for at least 3 hours or overnight before freezing in an ice cream maker according to the manufacturer's instructions.
- Once the custard is frozen, transfer it to a sturdy container with a tight-fitting lid and freeze for up to 2 months.