The name of this delicate dessert comes from the small lidded porcelain pots in which the desserts are traditionally baked.
Preheat oven to 300 degrees. Place six 4-ounce ovenproof ramekins or pots de creme in a 13-by-9-by-2-inch roasting pan; set aside.
Place 1/2 cup sugar in a medium saucepan set over medium heat. Cook, without stirring, until sugar has caramelized and is golden brown, about 3 minutes. Swirl pan, dissolving unmelted sugar; reduce heat to low.
Slowly and carefully whisk in the milk and 1 cup cream. Scrape the vanilla seeds into the pan and add the pod. Increase heat to medium-high and bring to a boil; remove the pan from heat.
In a medium bowl, whisk together remaining 1/4 cup sugar, egg yolks, and salt; continue whisking until pale yellow in color. Slowly add the hot cream mixture to the egg mixture, whisking constantly. Pour this new mixture through a fine sieve set over a large liquid measuring cup; discard vanilla pod.
Using a tablespoon or a small ladle, skim the surface to remove any visible air bubbles. Pour approximately 1/2 cup liquid into each ramekin. Fill roasting pan with hot water to within 1 inch of ramekin tops. Cover roasting pan with foil, and poke small holes in two opposite corners for vents.
Carefully place pan on center oven rack; bake until just set, about 35 minutes. Remove foil; transfer ramekins to a wire rack to cool completely. Cover with plastic wrap, and refrigerate.
When ready to serve, place the remaining 1/2 cup cream in a chilled mixing bowl. Using an electric mixer, whip cream until soft peaks form. Add a dollop of whipped cream to each serving.
Be careful not to overcook these treats; the custard should wiggle gently when shaken.