Instructions
Set a medium bowl in a large bowl of ice water.
Whisk the egg yolks in a medium bowl until pale and slightly thickened.
Pulse the coffee beans in a spice grinder until coarsely chopped.
Combine the coffee, cream, half-and-half, sugar, and salt in a medium saucepan.
Bring to a simmer over moderate heat and cook, whisking occasionally, until the sugar is dissolved and the mixture is steaming.
Slowly whisk half of the hot cream mixture into the egg yolks, then whisk the combined mixture back into the saucepan.
Cook over moderately low heat, stirring constantly, until the custard coats the back of a spoon; do not let it boil.
Transfer the custard to the bowl set in ice water, stir in the vanilla, and cool for 30 minutes, stirring occasionally.
Strain the custard into a bowl and refrigerate until very cold.
Whisk the chilled custard, transfer to the Ninja Creami tub, and freeze for 24 hours.
Remove the tub from the freezer, let thaw for 15 minutes, and process in the Ninja Creami.
Pro Tips
Do not let the custard boil during the cooking process to prevent curdling.
Stir the custard occasionally while cooling in the ice bath to ensure even temperature reduction.
Straining the custard ensures a smooth texture by removing the coarse coffee bean pieces.
Allowing the frozen tub to thaw for 15-30 minutes before processing helps achieve the best consistency.