Before cooking the custard, prepare an ice bath by putting ice cubes and water into a large bowl and placing a smaller bowl on top. This will stop the cooking and cool the ice cream base down more quickly and evenly.
In a medium saucepan, mix cream, 1/2 & 1/2, half of the sugar, and salt with a whisk, and bring to a simmer over medium heat, stirring occasionally (don't let it come to a boil). (If using a whole vanilla bean; Split the vanilla bean pod in half lengthwise, and carefully scrape out seeds with a sharp knife. Add the vanilla pod and scraped seeds to the cream and 1/2 & 1/2 with the sugar)
In a small bowl, whisk the egg yolks and the other 1/2 of the sugar together
When the 1/2 & 1/2 begins to bubble, remove from heat, and using a ladle, add a small amount of the hot cream mixture to the yolks, whisking constantly.
Continue adding small amounts of the hot cream to the yolks until you've added about 3/4 cup
Continue adding small amounts of the hot cream to the yolks until you've added about 3/4 cup.
Continue to cook, whisking constantly in a figure-eight pattern in order to incorporate all the mixture from the bottom and sides of the pan, about 5-7 minutes, or until the custard coats the back of a spoon. Stir in vanilla paste, if using, instead of vanilla pod. (Don't use both)
Remove custard mixture from heat, pour through a fine mesh sieve to remove any small bits of egg.
Transfer custard into a heat safe bowl and place in ice bath. Cover with plastic wrap and refrigerate until completely cold, several hours or overnight.
Follow the directions on your ice cream machine. Once it's done, the texture of the ice cream will have a creamy texture similar to soft serve.