Prepare the vanilla: Halve the vanilla bean lengthwise and scrape out the seeds with a paring knife. Position a rack in the middle of the oven and preheat to 325 degrees.
Infuse the cream: Bring the cream, half-and-half and vanilla seeds and pod to a simmer in a saucepan over medium heat. Reduce the heat to low and simmer to infuse the cream with the vanilla, 10 to 15 minutes. Discard the vanilla pod. Remove the cream mixture from the heat and cool slightly. Meanwhile, bring a kettle of water to a boil.
Make the custard.
Whisk the egg yolks, 1/2 cup sugar and the salt in a large bowl until the sugar dissolves and the mixture is pale yellow and thick; it should leave a trail when you lift the whisk. Pour in the cream mixture in a slow, steady stream, whisking constantly. Skim off any foam or bubbles from the surface.
Pour into ramekins: Arrange eight 6-ounce ramekins in a roasting pan and divide the custard evenly among them.
Bake in a water bath: Pull out the oven rack slightly, place the roasting pan on it and pour enough boiling water into the pan to come halfway up the sides of the ramekins.
Bake until the custards are just set in the center, 40 to 45 minutes. Carefully remove the ramekins from the water bath and transfer to the refrigerator. Chill, uncovered, at least 2 hours and up to 1 day.
Prepare the topping: About 30 minutes before serving, sprinkle 1 teaspoon sugar over each custard. Tilt the ramekins to evenly distribute the sugar and tap out any excess.
Caramelize the sugar: Holding a kitchen torch about three inches away, burn the sugar until it turns a deep amber. Refrigerate the creme brulees just until the crust hardens, 30 minutes to 1 hour, but not longer (the topping may start to soften). Serve cold.