Whisk together the egg yolks. Pour in a little of the hot coffee mixture and whisk in to temper the yolks, and then pour the egg mixture into the pot. Return to the heat, stirring constantly until the mixture is nappe, or thick enough to coat the back of a spoon. Strain the ice cream base into an ice bath. Chill overnight.
Freeze in an ice-cream machine according to manufacturers' instructions. Transfer to a container and freeze overnight.