1 ounce pistachio paste (recipe below)
1/2 cup sugar
2 tablespoons cornstarch
1/8 teaspoon salt (less if using salty nuts)
2 cups whole milk
2 large egg yolks
2 tablespoons butter, softened
1 teaspoon vanilla extract
1/2 cup pistachio nuts, chopped fine
1/3 cup pistachios
1/3 cup powdered sugar
2-4 tablespoons water
For paste: Grind the pistachios in a food processor for 1-2 minutes, until nearly a fine powder. Transfer to a bowl. Stir in sugar and water. (Err on the side of using too little liquid rather than too much; the paste should not look runny and should be easily held and shaped when in your hand.)
For pudding: Pour milk into a 2-quart saucepan and place over medium heat. Whisk in the pistachio paste and stir until the heat dissolves the paste into the milk. Combine the sugar, cornstarch and salt in a separate bowl. Slowly whisk into milk mixture immediately after pistachio paste dissolves. Stir constantly, until mixture thickens and begins to boil.
In another bowl, whisk the two egg yolks together. Take 1/2 cup of the thickened pudding and whisk to combine with the egg yolks. Once combined, immediately pour egg mixture back into the pudding in the saucepan. Boil for 1 minute, whisking as it cooks. Remove from heat; add the butter, vanilla and chopped pistachios. Mix thoroughly and chill well.