Preheat the oven to 180 degrees Celsius and line a baking tray with baking paper.
In a large mixing bowl, sift through the flour, add the baking powder and mix until combined. In a small bowl, whisk the eggs with the vanilla extract. Add the egg mixture to the flour mixture and stir until just combined. Add the shelled pistachios and ensure they are well incorporated into the dough.
On a floured surface, pour the dough from the bowl and lightly knead it until the clumps are removed.
Form the dough into a log shape and place gently on a baking tray and put in the oven for approximately 25 minutes, or until slightly firm. Keep oven turned on.
Remove the log shaped dough from the oven and allow to cool completely.
Once cooled, slice the dough into thin slices (about 1 cm each) and spread out back into the baking tray and put it back in the oven for a further 10 minutes.