Place a medium pot over medium-high heat, and whisk together the milk, sugar, and 1 cup of the heavy cream.
Use a spoon or the back of a butter knife to scrape the seeds from the vanilla bean into the pot. Add the vanilla bean to the pot, too.
HEAT MILK MIXTURE:
Heat the mixture, while stirring often, until the mixture reaches 110 degrees.
Cover the pot and let the mixture cool for about 25 minutes, or until it cools to 80 degrees.
MIX CUSTARD MIXTURE:
Remove the vanilla bean and add the egg yolks to the pot and whisk it into the warm milk mixture until combined.
COOK CUSTARD MIXTURE:
Place the pot back on the stove and heat it over medium heat. Cook, while stirring constantly (make sure you scrape all around the bottom of the pan and edges).
Cook until the mixture reaches 170-175 degrees F on an instant-read thermometer. The mixture will be thickened enough to coat the back of a spoon. Remove the pot from the heat.
STRAIN:
Place a fine-mesh strainer over a medium bowl and pour the custard mixture through the strainer.
MIX AND CHILL:
Whisk in the remaining cup of heavy cream and vanilla extract. Cool the mixture for 10 minutes, and then cover it and refrigerate for at least 2 hours, or overnight.
CHURN AND FREEZE:
Churn in an ice cream maker as per the manufacturer’s instructions. Churn until custard resembles soft-serve ice cream.
Transfer the frozen custard to an airtight container and freeze for 3 hours.