"If you don't have vanilla beans, you can substitute 1 tablespoon pure vanilla extract or 1 tablespoon of the vanilla bean paste...but promise me you'll eventually try it with real, live vanilla beans. Also, if using vanilla bean seeds or paste, you can strain the mixture before adding it to the egg yolk mixture. Because the little vanilla bean seeds tend to settle after baking, straining gets rid of the excess amount. I never do this. I'm too lazy and I don't mind the vanilla bean seeds floating in the luxurious cream mixture. You can certainly use all 4 cups of heavy cream instead of subbing in the 1 cup milk but for some reason, I love this ratio of heavy cream and milk (I usually use 1%). It's still very rich and creamy. Last thing, I promise, if you have vanilla sugar laying around (empty vanilla bean pods set in granulated sugar and covered make amazing vanilla sugar), sub it in for the granulated sugar in the cream mixture and also for the topping to be caramelized. Amazing...."