1. Bring a pot of water to boil.
2. Blanch the pistachios for 20 to 30 seconds.
3. Drain and pat dry.
4. Spread onto a lined sheet tray and allow to dry overnight.
5. Grind the pistachios in a food processor being careful not to allow the nuts to turn to butter. Sift the flour. Any large pieces that remain, return to the food processor and grind again.
6. Alternately, once the pistachios have dried, roast in the oven at 300°F for 5 to 7 minutes, stirring regularly. Allow to cool. Follow step #5