If using a vanilla bean, split it lengthwise and scrape out the seeds. Add both the pod and seeds to a heavy-bottomed saucepan. In the same saucepan, combine the heavy cream, whole milk, 1/2 cup of the granulated sugar, and salt. Heat over medium heat, stirring occasionally, until the mixture is hot and steamy, just barely simmering around the edges (do not boil). Remove from heat. If using a vanilla bean, let it steep for 10-15 minutes, then remove and discard the pod before proceeding.

In a separate medium bowl, whisk the egg yolks with the remaining 1/4 cup of granulated sugar until light yellow and creamy.

Slowly ladle about 1 cup of the hot cream mixture into the egg yolk mixture, whisking constantly to temper the yolks. This gradually raises the temperature of the eggs, preventing them from scrambling.

Pour the tempered egg yolk mixture back into the saucepan with the remaining hot cream mixture. Return the saucepan to medium-low heat. Cook, stirring constantly with a wooden spoon or spatula, until the custard thickens enough to coat the back of the spoon (it should reach about 175-180°F or 80-82°C on an instant-read thermometer). Do not boil, as this can curdle the eggs.

Immediately remove the saucepan from the heat. Pour the custard through a fine-mesh sieve into a clean bowl. This removes any small bits of cooked egg and ensures a silky-smooth texture. If using vanilla extract, stir it into the warm strained custard now.

Place the bowl of custard into a larger bowl filled with ice and water (an ice bath) to cool it down quickly. Stir occasionally. Once cooled to room temperature, cover the bowl tightly with plastic wrap and refrigerate for at least 4 hours, or preferably overnight, until completely chilled. This is crucial for optimal ice cream texture.

Once the custard is thoroughly chilled, pour it into your ice cream maker's pre-frozen freezer bowl and churn according to the manufacturer's instructions, usually 20-25 minutes, until it reaches the consistency of soft-serve ice cream.

Transfer the soft ice cream to a freezer-safe airtight container. Press a piece of plastic wrap directly onto the surface of the ice cream to prevent ice crystals from forming. Freeze for another 2-4 hours, or until firm, before serving. Enjoy!