In a saucepan, combine heavy cream, whole milk, sugar, and instant coffee granules. Heat over medium heat until the mixture is hot but not boiling.

In a mixing bowl, whisk the egg yolks until they are pale and slightly thickened.

Slowly pour the hot cream mixture into the egg yolks, whisking constantly to temper the yolks.

Return the mixture to the saucepan and cook over low heat, stirring constantly until it thickens enough to coat the back of a spoon.

Remove from heat and stir in vanilla extract. Let the mixture cool to room temperature, then refrigerate until chilled.

Once the mixture is chilled, pour it into an ice cream maker and churn according to the manufacturer's instructions until it reaches a soft-serve consistency.

Transfer the ice cream to a lidded container and freeze for at least 2 hours to firm up.