Start by splitting the vanilla bean down the center. Scrape out all the seeds and place in a large bowl. Take the vanilla bean pod and place it in a small pot with sea salt and heavy cream.
Preheat the oven to 300 degrees F. Heat the heavy cream mixture just until the cream is simmering. Do not boil! Remove from the stovetop and set aside to slightly cool. Remove the vanilla bean pod (If using vanilla extract, stir it in here).
In the bowl with the vanilla bean seeds, add the egg yolks (I like to save the whites in a container for omelets during the week!) and 1/2 cup sugar. Beat until the mixture is light, about 2-3 minutes. Meanwhile, place 6 cups of water in a large pot and heat to boiling.
Add about 1/4 of the cream mixture into the egg and sugar mixture. Mix until combined. Then pour the (now-tempered) egg + sugar mixture into the remaining heavy cream mixture. Stir until combined.
Remove the chocolate-filled ramekins from the freezer and place them in a metal 9x13 baking pan. Pour the prepared mixture evenly into the ramekins. (You should use up all the mixture between the 6 dishes.)
Fill the baking pan with boiling water halfway up the sides of the ramekins. Bake for 30-35 minutes or until centers are barely set (very slight jiggle). Cool completely at room temperature and then refrigerate for 3-4 hours before serving. Alternatively, these can be refrigerated 4-5 days before use.
When ready to serve, sprinkle the remaining 1/4 cup superfine sugar on top of the custards. I find it helpful to use a little more sugar than needed to swirl the dish around and make sure the top is evenly coated with sugar (then just pour the extra sugar onto the next ramekin). Use a kitchen torch to heat the tops until the sugar melts and browns (or even slightly blackens) a bit. Top with fresh berries and enjoy immediately.
Alternatively, if you want to use your oven, move the oven rack to the top position and heat the oven to a high broil. Once the oven is heated, add the custards topped with superfine sugar to a tray. Place the tray on that top shelf and watch carefully as they broil. It only takes 1-3 minutes, so watch closely to avoid burned crèmes brûlée.