4 large egg yolks 1/2 cup plus 2 tablespoons granulated sugar 2 cups heavy cream 1 vanilla bean, split lengthwise and scraped 1/4 cup air-dried light brown sugar (see Tip)
Preheat oven to 275º F.
In a medium bowl, whisk the egg yolks with half of the granulated sugar. In a small saucepan, warm the heavy cream with the vanilla-bean scrapings and the remaining granulated sugar until the cream is steaming. Gradually whisk the hot cream into the egg-yolk mixture until blended. Strain the custard and pour it into four 5-ounce ramekins or shallow gratin dishes.
Set the ramekins in a small baking dish and add enough hot tap water to the dish to reach halfway up the sides of the ramekins. Bake for about 1 hour and 15 minutes, or until the custards are just set. Let the custards cool in the water bath for 10 minutes, then remove from the baking dish and allow them to cool completely. Cover and refrigerate for at least 4 hours or overnight.
Preheat the broiler. Sift a thin even layer of the air-dried brown sugar over each of the custards. Broil one ramekin at a time as close as possible to the heat source until the brown sugar melts, forming a caramelized crust on top of the custard. Serve immediately.
To air-dry brown sugar, sift it onto a plate and leave it out, uncovered, for 1 day. Alternatively, if the weather is humid, the sifted brown sugar can also be dried in the oven. Set the temperature at 250ºF and put the sugar in the oven for 20 minutes.