Whisk egg yolks together in a medium bowl or large 4 cup glass measuring cup until creamy and bright. Set aside.
In a heavy bottomed sauce pan add the milk, heavy cream, sugar, vanilla and salt.
Stir on medium low until sugar is dissolved and milk is just beginning to get hot. Do not let it boil or create a film on the top.
Note: If you've never made a custard before, you might wonder about "tempering." This recipe is a custard which means it has eggs in it. It is not a vegan ice cream. When eggs get hot, they cook. We DO NOT want our eggs to scramble. We DO want them to become silky smooth and help the hot cream become a thick rich custard. Tempering is the process of very slowly warming the eggs to the temperature of the hot milk without scrambling them. Temper the egg yolks by very slowly drizzling or ladling 1 cup of the hot milk mixture into the egg yolks, whisking constantly. Once the milk and eggs are fully incorporated, slowly add the tempered egg and milk mixture back into the saucepan of remaining hot milk.
Turn the heat up to medium and stir constantly until the custard coats the back of a spoon.
Turn off the heat and allow to cool. Once ice cream is cool stir in alcohol, if using. This is also the time to stir in any flavors that you want to add. (Ideas: Chopped strawberries, peaches, bananas, berries, cream cheese, chocolate, cocoa, chocolate chips, espresso powder, macha, nuts, marshmallows. The options are endless.)
Cover the pot and put it into the refrigerator. (I like to do this to continue to slowly drop the temperature of the custard. This keeps ice crystals from forming too fast and making your ice cream icy. Slow chilling before churning makes for a creamier cream.) Allow to chill for an hour or overnight. Pour the chilled cream mixture into prepared ice cream maker. Churn according to manufacturer instructions.
Scoop into bowls and be happy.