Preheat the oven to 170C (325F). Line a baking sheet with a silpat liner or parchment paper.
Grind 90 grams of the pistachios finely and set aside. Chop the remaining 100 grams roughly and place in a plate or flat bowl for rolling.
Put the finely ground pistachios, almond meal, sugar, egg whites, optional orange blossom water and optional food colouring in a large bowl. Mix just until the batter is moistened, do not over beat. If the batter is too moist, add a little more almond meal.
Form one tablespoon of the batter into balls and roll in the chopped pistachios. Place the cookies about 2 centimeters (3/4 inch) apart and bake for approximately 13 minutes. Let cook for 10 minutes before moving to a baking rack. Dust with icing sugar, when cooled.