Vanilla Custard Ice Cream-Kem Vanilla

This recipes is based on David Lebovitz's  and Melissa Clark's. Two kinds of vanilla here is not a mistake but they help to boost the vanilla flavor.
Make 1 quart
  2 cup heavy cream
  1 cup whole milk
  3/4 cup sugar
  1 pinch of salt or 1/8 tsp fine sea salt
  6 egg yolks
  1 vanilla bean, split in half lengthwise, scrape the seeds
  3/4 tsp vanilla extract

1. Combine heavy cream, milk,  and sugar in a medium sauce pan.  Scrape the seeds out of vanilla bean and add both seeds and bean to the mixture.  Bring it to a gentle boil, stir often over medium high heat.  Remove from heat, cover and let it steep at room temperature  30 minutes.
2. Whisk the egg yolks in a medium bowl until  slightly thickening and light in color.  Continue whisking constantly and slowly add warm milk mixture into egg yolks. 
3.  Pour the mixture back to the saucepan.  Stir the mixture constantly over medium heat with a heatproof spatula.Scrape the bottom often until the mixture is just thick enough to coat the back of spatula about 170 oF to 185 oF.  Pour the custard through a fine sieve to a bowl.  Add vanilla extract and vanilla bean back to the custard.  Let the mixture cool down at room temperature or stir to cool over an ice bath.  Cover and chill the mixture overnight in the fridge.
4. Remove the vanilla bean before churning, wash and save for other use.  Churn and freeze as manufacturer's instruction of your ice cream machine.  Transfer the ice cream to an airtight container and freeze overnight before serving.