If your ice cream maker needs it's bowl frozen, place in freezer for the specified time by the manufacturer - I usually do this for 24 hours.
Place the 4 egg yolks into a medium sized mixing bowl.
Add 2/3 cup of white sugar into the mixing bowl and beat together with a hand mixer or whisk until the eggs become a pale yellow color and the mixture is thick - about 2 minutes. Set bowl aside.
Add 2 cups of whole milk to a medium sized saucepan.
Slice the vanilla bean in half lengthwise, and with the dull side of a knife scrape the seeds out and place them into the saucepan along with the empty vanilla bean pod.
Heat the milk over medium heat while stirring occasionally. Once the milk begins to let off steam, remove from the heat (about 185F). Do not boil the milk.
Temper the yolk/sugar mixture by slowly pouring in 1/2 cup of the hot milk into the yolk mixture while continuously whisking the yolks. See Note 2.
Now add the warmed yolk mixture into the saucepan with the rest of the hot milk while whisking the hot milk mixture continuously. Heat the mixture on medium heat with constant stirring with a wooden spoon until the mixture coats the back of the spoon or it reaches 185 F.
Remove from the heat.
Pour custard through a fine mesh sieve. This will remove any egg chunks that may have formed leaving you with a silky smooth custard - I don't recommend skipping this step.
Stir in 1 cup heavy cream (whipping cream) and 2 teaspoons vanilla extract.
Allow to cool to room temperature on the counter for about 30 minutes.
Cover with a plastic wrap and allow to completely cool in the fridge - can take around 4 hours, you can even leave it overnight.
Follow the manufacturer's instructions for your ice cream maker. I have to make sure my paddle is turning before I add in my cooled custard. I allow it to churn for about 20 minutes. At this point, it is the consistency of soft serve.
Scoop it out of the ice cream maker as per manufacturer's instructions and place into a freezer safe container. Place a cover on and then into the freezer for four hours. The extra freezer time allows the vanilla gelato to firm up.
Once set up, scoop, serve, and enjoy!