Preheat the oven to 325 degrees F.
Add the heavy cream and salt to a medium saucepan and heat over medium heat just until simmering. As soon as it begins to simmer (don’t let it boil!), remove from heat and stir in the vanilla extract. Set aside to cool for 10 minutes.
Meanwhile, bring about 5 cups of water to a boil on the stovetop to use later in the water bath (I use a large saucepan so it boils more quickly). Place either (8) 4-ounce ramekins, (6) 5-ounce ramekins (my fav), or (5) 6-ounce ramekins in a roasting pan or two smaller baking pans; set aside.
Add the egg yolks and 1/2 cup granulated sugar to a mixing bowl. Beat on medium speed for 2 minutes.
Using a hand whisk and whisking constantly, slowly drizzle 1/4 cup (eyeball it) warmed heavy cream into the egg mixture; whisk until completely incorporated. Repeat with another ¼ cup warmed cream. Once combined, slowly whisk in the remaining warmed cream until combined, whisking constantly.
Pour the custard into a large liquid measuring cup (or pitcher)— this makes filling the ramekins much easier. Evenly divide the custard between the ramekins. Transfer boiling water to a separate (or cleaned) liquid measuring cup or pitcher.
Transfer the roasting pan with custard to the middle oven rack then immediately pour the hot water into the pan around the custard until it reaches about ¾ up the sides of the ramekins. (Place the spout on the corner of the roasting pan and pour slowly so water doesn't splatter onto the custard.)
Bake at 325 degrees F for 25-45 minutes or until the center registers 170 degrees F on an instant read thermometer. The custard should be barely set, not liquid, but still jiggly all over. The baking time will depend on the depth of the ramekins; shallow 1-inch ramekins (5-6 ounces) will take closer to 25 minutes, deep 2-inch ramekins (4 ounces) will take closer to 45 minutes).
Remove the custards using tongs to a cooling rack and let cool to room temperature, 1-2 hours. Cover custards with plastic wrap and refrigerate for 4 hours up to 3 days before adding the sugar topping.