Lightly coat an 8-inch pan with cooking spray. Line with parchment paper, leaving a small overhang. Pour in chocolate and smooth with a spatula into an even layer.
Sprinkle with pistachios and sea salt. Chill in fridge until completely set, about 30 minutes. Peel off parchment, and break into pieces.
I have made this recipe twice. It has been a huge success and it couldn't be easier to make. Perfect as a gift in a nice little box or tin.