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

In a mixing bowl, whisk the egg yolks. Slowly pour the hot cream mixture into the egg yolks while 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 (about 10-15 minutes).

Remove from heat and stir in the vanilla extract. Let the mixture cool to room temperature, then refrigerate until completely chilled (about 2 hours).

Once chilled, pour the mixture 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 an airtight container and freeze for at least 2 hours to firm up before serving.