Preheat oven to 325°F. Bring a medium pot of water to a boil for the water bath that will be used to bake the custard.
In a medium bowl, whisk egg yolks and sugar until mixture is a pale yellow, about 2-3 minutes. Set aside.
In a small saucepan, heat heavy cream and salt over medium heat until bubbles form around sides of pan.
Remove from heat and stir in vanilla extract. Then whisk a small amount of cream into egg mixture to temper eggs.
Whisk continuously while adding small amounts of the rest of cream into eggs.