For the creme anglaise: Place the half-and-half in a small, heavy saucepan. Using a sharp paring knife, carefully split the vanilla beans lengthwise and scrape the seeds into the cream, then add the hulls. Set the pan over medium heat and, stirring occasionally, bring the cream to a bare simmer. Off the heat, allow the cream to infuse for about 10 minutes.
Meanwhile, whisk the egg yolks, sugar and salt in a medium, heavy, heat-proof bowl until light and frothy, about 2 minutes. Secure the bowl in position by wrapping a damp kitchen towel around the base. Remove the vanilla bean hulls from the warm cream mixture. Whisking constantly, very slowly and gradually pour the cream mixture into the yolk mixture until it is all incorporated.
Rinse, but don't dry, the saucepan. Pour the cream and egg mixture into the pan, set it over medium-low heat and cook, stirring constantly, until the mixture thickens and coats a wooden spoon to the degree that you leave a crisp-edged, clear trail when you draw your finger across the back of a spoon, about 12 minutes.
Set a fine-mesh sieve over a medium bowl and strain the custard into it. Cover with a piece of plastic wrap, pressing it right onto the surface of the custard and poking several holes with the tip of a paring knife for the steam to escape. Allow the custard to cool to lukewarm and then refrigerate until well-chilled, at least 4 hours and up to 4 days.
To assemble: Place 1 cup of the chilled creme anglaise and the ice cream in a blender and pulse several times to begin breaking up the ice cream. With the motor off, use a flexible spatula to mash the mixture down onto the blender blade. Continue pulsing, stopping and mashing until the mixture is well-blended, thick and moving easily in the blender jar, roughly 30 to 90 seconds. Pour into a chilled glasses, garnish and serve at once.
