Line a baking sheet with parchment paper
Pre-heat the oven to 375 degrees
Put egg white in a clean bowl and beat till stiff peaks are formed
Add sugar and orange zest
Add half the butter and flour and fold into the mixture
Add the remaining butter and flour and fold into the mixture
Drop 1 tsp of batter on the parchment paper and with the back of a teaspoon, spread it into 6" rounds
Sprinkle pistachios on top
Leave some space in between the two rounds as these will spread during baking
Bake for 7 minutes at 375 degrees
Take out from the oven and with the help of a spatula, remove the cookie and wrap around a rolling pin, with the pistachios on the outer side
You have to be fast in this step as the cookies cool and become crisp, so they can break
Cool on a wire rack completely before storing them