Preheat the oven to 325° and arrange the ramekins in a large, rimmed baking pan.
In a medium saucepan over moderately high heat, combine the heavy cream, ½ of the sugar, the vanilla bean seeds and pod, and the salt and bring to a boil, stirring to dissolve the sugar.
While the cream is heating, add remaining sugar to the egg yolks and whisk to combine.
Gradually add about 1/3 of the hot cream to the yolks, whisking constantly so the eggs don't cook, then add the remaining hot cream and stir to fully combine.
Strain the custard through a fine mesh sieve into a clean bowl.
Carefully ladle or pour the custard into the ramekins, filling them to the rim.
Place the baking pan in the oven and carefully pour enough hot water into the pan to reach halfway up the sides of the ramekins.
Bake until the edges have set but the center still jiggles when the pan is gently shaken, 20-25 minutes.
Remove the ramekins from the water bath and let cool on a rack for 30 minutes. Then wrap individually and refrigerate for at least 3 hours.
To serve, sprinkle the top of each custard with a thin even layer of vanilla sugar, using about one tablespoon per ramekin.
Use a kitchen blowtorch or the broiler to evenly melt and caramelize the sugar. If using the broiler, keep a careful eye as the sugar can go from beautiful brown to burnt in seconds.
Garnish each ramekin with 3 raspberries and a sprig of mint, if desired.
Serve immediately.