Combine the whole milk and double cream in a saucepan, heating it over low heat until it becomes warm but not boiling. Remove the saucepan from the heat.
In a separate bowl, whisk together the granulated sugar, instant coffee granules, and egg yolks until they are thoroughly blended.
Gradually pour the warm milk and cream mixture into the egg mixture, ensuring a continuous whisking motion to prevent curdling.
Return the combined mixture to the saucepan and cook it over low heat while constantly stirring. Continue until it thickens sufficiently to coat the back of a spoon, typically taking about 5-7 minutes. Make sure not to allow it to reach a boiling point.
Take the mixture off the heat and incorporate the vanilla extract by stirring it in.
Allow the mixture to cool down to room temperature, then cover it and refrigerate for a minimum of 4 hours, or until it is completely chilled.
Once chilled, transfer the mixture into an ice cream maker and churn according to the manufacturer’s instructions.
After churning, move the ice cream into an airtight container and place it in the freezer for an additional 2 hours to achieve a firmer consistency.
Enjoy your homemade Coffee Ice Cream by serving it in bowls or cones!