Pour the heavy cream, vanilla and pistachios into a pot and place over medium heat. Bring the cream to a simmer, do not boil.
In a large bowl, whisk together egg yolks and sugar until the sugar dissolves and the mixture is a lemon colour. Temper the yolks by gradually whisking in the hot cream into the yolks and sugar mixture. Do not add the hot cream too quickly or the eggs will cook. Place mixture into a blender and puree until smooth. Pass the mixture through a fine strainer, discarding any solids.
Preheat oven to 350.
Pour the mixture into 6 - 8 oz ramekins, filling them three quarters of the way up. Fill a large shallow baking pan with 1/2" warm water. Carefully place the ramekins in the water bath and bake for about 35 minutes; the centre should just wiggle slightly.
Remove the pan from the oven and let the ramekins cool in the water for about 10 minutes. Then put them in the fridge for at least 2 hours to chill.