In a medium saucepan over medium heat, heat up the milk, heavy cream and vanilla extract to 160°F. Stir well.
Combine the sugar, salt, flour and cornstarch in a medium mixing bowl. Stir until incorporated and set aside.
In a large metal mixing bowl, whisk the egg yolks.
While constantly stirring, very slowly pour ½ cup of the milk mixture into the eggs.
Very slowly pour in another ½ cup of the milk mixture while whisking.
Slowly whisk in the dry ingredients.
Pour the mixture from the mixing bowl back into the saucepan, stirring constantly.
Cook over medium heat, stirring slowly and constantly, until the mixture is thick. Remove from the heat and cool to room temperature.
Transfer to an airtight container and refrigerate until completely cold. Garnish with chopped pistachios and serve.