In a bowl, add the ground pistachios, flour, icing sugar, and salt and whisk together until combined.
100 gs ground pistachios, 165 gs all-purpose flour, 40 gs icing sugar, 1/2 tsp salt
Cut the cold butter into small pieces and add to the dry ingredients mix. Using your electric or hand beater, mix the butter in the dry ingredients until it reaches a breadcrumb-like consistency. Make sure that the butter is cold, or the dough will become too soft.
113 gs unsalted butter, cold
Now, gradually add the cold water into the dough, adding only a little at a time, and mix until the dough just holds its shape together. Be careful not to add too much water at once. Too much water will make the dough sticky and difficult to work with.
20-30 ml cold water
Tightly wrap the dough in cling film and let it chill in the fridge for at least 30 minutes. After chilling, roll the dough between two sheets of baking paper (so that it does not stick to the rolling pin), and shape it according to your tart ring or pan. If you are setting the dessert in a regular glass dish, cut out the tart in the shape of the base of the dish, bake it, then place it on the bottom og the dish.
Bake the tart base at 180 degrees celsius for 15 minutes if using a small tart ring, or 20-25 minutes if using a big tart pan. Let the tart base cool before adding the filling.