In your food processor pulse 3 oz of the pistachios and 1/4 c sugar until a fine paste is achieved, about 1 minute.
Chop the remaining 3 oz of nuts and set aside.
In a mixing bowl whisk together the egg yolks, remaining sugar and heavy cream until a thick, smooth texture is achieved.
In a saucepan over medium heat, cook the milk and pistachio paste until it just starts to simmer, stir frequently, but do not let it boil.
Whisking constantly, add 1/4 of the milk mixture to the yolk mixture to temper the eggs.
Whisk the tempered yolk mixture back into the milk mixture and cook for about 5 minutes, just until it begins to simmer.
Push the custard through a mesh sieve and discard the solids.
Transfer the mixture to a bowl that is placed in a water bath and let cool to room temperature, about 45 minutes - 1 hour.
Place a sheet of plastic wrap directly on the top of the custard, to prevent a skin from forming.
Cover tightly and refrigerate 3 hours, or overnight.
Freeze the custard according to manufactures directions for your ice cream maker, about 25-30 minutes, adding the remaining chopped pistachios a minute or two before finished.
Serve immediately or for a firmer texture freeze in an airtight container.
Notes
Recipe from Williams-Sonoma Frozen Desserts
Coursesdessert, ice cream
Recipe by It Bakes Me Happy at http://itbakesmehappy.com/2014/03/pistachio-gelato.html