In a medium pot, combine the milk, cream and vanilla bean. Bring the mixture to a simmer, then shut off the heat. Cover and steep for one hour.
Grind the sugar and basil leaves together in the bowl of a food processor. Put the egg yolks into a medium bowl, then whisk in the basil sugar, reserved vanilla seeds and salt.
Preheat the oven to 300° and return the milk/cream to a simmer. Remove the vanilla pod and carefully ladle some of the hot cream into the eggs. Whisk the warm egg mixture into the pot of milk/cream.
Cook the mixture over medium-low heat, stirring constantly until it reaches about 140°.
Pour the mixture through a sieve into a medium bowl and portion the strained custard evenly between ramekins. Place them in a baking pan filled with hot water, cover with foil and bake at 300° for 30-45 minutes.
Allow the custards to cool, then refrigerate for at least 6 hours before serving.