In a medium-size saucepan, add the heavy shipping cream and butter.
Heat on the stove top over medium heat and stir constantly until the butter is melted and the heavy cream starts to bubble, but not boil.
Remove from heat; add the chocolate chips to the cream mixture and allow it to sit untouched for 5 minutes.
After 5 minutes, start to whisk vigorously until the chocolate is smooth.
In a food processor, grind the pistachios to fine crumbs.
Stir the pistachios into the chocolate mixture until well combined.
Cover and refrigerate for 2 hours, or until the filling is firm.
Once the filling is firm, use a melon baller or a small cookie scoop to roll the filling into balls about 2 teaspoons in size.
Freeze for 15 to 30 minutes.