Prepare the Coffee Base: Brew 1/2 cup of strong coffee or espresso and set aside to cool slightly.
Make the Custard Base: In a saucepan, combine the heavy cream and whole milk. Heat over medium heat until the mixture is hot but not boiling.
Whisk Egg Yolks and Sugar: In a mixing bowl, whisk together the egg yolks and granulated sugar until smooth and slightly pale.
Temper the Eggs: Gradually pour about half of the hot milk mixture into the egg yolks while whisking constantly. Then pour the egg mixture back into the saucepan with the remaining hot milk mixture.
Cook the Custard: Stir constantly over low heat for 5–7 minutes until the custard thickens and coats the back of the spatula.
Add Coffee and Vanilla: Remove from heat and stir in the brewed coffee and vanilla extract. Mix until well combined.
Strain the Custard: Pour the custard through a fine mesh strainer to remove any curdled egg bits.
Chill the Custard: Let the mixture cool to room temperature, then cover and refrigerate for at least 4 hours or overnight.
Churn the Ice Cream: Once chilled, pour the custard into an ice cream maker and churn according to the manufacturer’s instructions (about 20–25 minutes).
Freeze Until Firm: Transfer the churned ice cream to an airtight container and freeze for at least 4 hours or until firm.