Over medium low heat, combine creams into a heavy bottom sauce pan, stirring frequently.
In a large bowl, combine egg yolks, sugar, and salt. Beat until well incorporated If you are doing chocolate ice cream, now is the time to add the cocoa poder to the warmed milk.
Once the milk has reached a simmer, turn heat down to low. Temper the egg yolks by adding small ladles of the warm cream mixture to the eggs.
Once you have incorporated 1/2 the cream mixture into the bowl, return the egg and cream mix to the sauce pan. Turn back up to medium low heat and whisk until the mixture gets to a very thick consistency and will generously coat a spoon.
Remove from heat, place in a heat resistant container and allow to cool for 45 minutes.
At this point place in to refrigerator and cool over night.
Add pureed fruit when cooled.
The next day, use your ice cream machine directions and freeze over night.