Place the pistachios and 2/3 cup sugar in a blender or food processor. Pulse until the pistachios are a fine powder. Add 1/2 cup milk and pulse until the mixture is thick and smooth like a paste. Set aside
For the Ice Cream Base
1. Pour 2 cups heavy cream, 1 cup milk, and 1 cup of sugar into a saucepan. Bring mixture to a simmer, and whisk until sugar has dissolved. 2. Whisk egg yolks in a medium bowl. Slowly whisk about half of the warm milk mixture into the egg yolks. Whisking constantly to prevent the eggs from curdling. 3. Pour the egg mixture back into the saucepan and cook over low heat, stirring constantly until custard begins to thicken. It should be thick enough to coat the back of a spoon, and hold a line drawn through with your finger. ** Do not bring the mixture to a boil, the eggs will curdle. 4. Pour pistachio paste, almond extract, and vanilla extract into a medium bowl. Strain ice cream base into the pistachio paste, and whisk. ** For a creamier texture, you can strain the mixture again and discard the pistachio pieces. 5. Cool the custard until completely cooled. Then freeze the custard according to the directions of your ice cream maker.