When you're ready to eat your popsicles melt the chocolate first. My favourite way to melt chocolate is to just break it into small pieces in a bowl and to microwave it in small increments (20 seconds), stirring in between, till it's completely molten. You could also melt the chocolate au bain marie on the stove.
Then have the other decoration ingredients ready - crushed pistachios, lemon zest or anything else you'd like to use
Take the popsicles out of the freezer and out of the molds. You may have to wait a minute for the mold to warm up enough to release the popsicles.
Drizzle some chocolate on the popsicles and right away sprinkle your pistachios and/or lemon zest on it cause the chocolate will set very fast on the cold popsicles and once it's set the nuts and zest will not stick so much anymore. You could also dip the popsicle partly or completely in the chocolate.
And that's it! Enjoy!!