Because the oil in the pistachio paste separates from the solids, it is necessary to blend the contents of the entire can of paste in a food processor until it is creamy and light in texture.
Ingredients
4 large egg yolks
1/4 cup sugar
1 1/2 tablespoons water
2 tablespoons well-blended pistachio paste
1 cup chilled heavy cream
Special equipment: an instant-read thermometer
Directions
Beat together yolks, sugar, and water in a metal bowl set over a saucepan of simmering water with a hand-held electric mixer at high speed until thick, pale, and registers 140°F on thermometer. Continue beating over simmering water, maintaining 140°F, 3 minutes more.
Remove bowl from heat and gradually add pistachio paste, beating until incorporated. Chill until cold, about 15 minutes.
Beat cream with cleaned beaters until it just holds stiff peaks. Stir one third of cream into pistachio base to lighten, then fold in remaining cream gently but thoroughly. Scrape into an airtight container and freeze until firm, about 4 hours.
