For the soup: Pick over the shelled pistachios to be sure there are no broken shells or other particles in them, then grind in a food processor or spice spice grinder until very smooth. Set aside.
Heat the oil in a medium-sized enamled cast-iron pot over medium heat. Add the onion, leek and garlic, and sauté for 5 minutes. Add the salt, pepper, turmeric, cu