Using a chef's knife or other large knife chop the white chocolate rather finely and place in a double boiler over medium heat along with the cream.
Using a microplane grater, zest one lemon into the chocolate/cream mixture. Steer clear of the bitter white pith.
Stir chocolate mixture occasionally while waiting for the chocolate to melt .
As soon as a smooth mixture forms, remove from the heat and allow mixture to cool slightly.
Place chocolate/cream mixture in the fridge for at least two hours or until completely solid.
After two or so hours, remove the now solid mixture from the fridge and allow to warm up for about 5-10 minutes at room temperature.
Using a metal spoon, melon baller or similar dig out a tablespoon of the mixture (some force will be required here) and use your hands to quickly form it into the shape of a ball. Then deposit onto a tray, a piece of parchment paper or similar.
Fair warning: The heat from your hands will melt the mixture quicker than you think. Work quickly. This will be messy. But fun! ;)
Repeat with the rest of the mixture until you have 6-10 white chocolate truffles.
On a cutting board or other large, clean surface, spread the chopped pistachios into a thin layer, then sprinkle another thin layer of popping candy (if using) on top.
One by one, roll the chocolate truffles in the popping candy/pistachio mass to form an even coating. There will be some popping and hissing as you do.
Pop onto a tray or serving platter and serve immediately or keep in the fridge for up to a few hours.