How to Make It
Set a medium bowl in a large bowl of ice water. In another medium bowl, whisk the egg yolks until pale and slightly thickened, about 2 minutes.
In a spice grinder, pulse the coffee beans until coarsely chopped. In a medium saucepan, combine the coffee with the cream, half-and-half, sugar and salt. Bring to a simmer and cook over moderate heat, whisking occasionally, until the sugar is completely dissolved and the cream mixture is steaming, about 7 minutes. Very gradually whisk half of the hot cream mixture into the beaten egg yolks in a thin stream, then whisk this mixture into the saucepan. Cook over moderately low heat, stirring constantly with a rubber spatula, until the custard is thick enough to lightly coat the back of the spoon, about 7 minutes; don’t let it boil.
Transfer the custard to the bowl set in the ice water, stir in the vanilla and let cool for about 30 minutes, stirring occasionally. Pour the custard through a fine-mesh strainer into another medium bowl and refrigerate until very cold, about 1 hour.
Whisk the chilled custard a few times, then scrape it into an ice cream maker. Freeze according to the manufacturer’s instructions. Transfer the ice cream to a plastic container, cover and freeze until firm, at least 3 hours.