Using a sharp knife, slice each vanilla bean lengthwise.

Using the back of the knife, scrap the seeds out of the halved vanilla beans.

Using a medium saucepan, add vanilla beans and half-and-half. Heat over medium-low, stirring occasionally, until it just begins to simmer.

Meanwhile, using a separate bowl, whisk together the sugar and egg yolks until well blended.

Gradually pour the heated half-and-half into the egg yolk mixture; whisking vigorously the entire time.

Transfer this mixture back into the saucepan and cook over medium-low heat, stirring constantly, until custard thickens noticeably and coats a wooden spoon. (~4-6 minutes).

Once the custard mixture has thickened, remove from heat and add the heavy cream; stir until well combined.

Pour mixture through a fine-mesh strainer into a clean container. Cover with plastic wrap, pressing the plastic directly onto the surface of the mixture, and refrigerate at least 1 hour, or overnight.

Pour the mixture into an ice cream maker and freeze according to the manufacturer's directions. (Note: For a softer ice cream, serve immediately. For a harder ice cream, transfer mixture into a freezer-safe container and freeze for 3-4 hours.)