Place flour, salt, sugar, pistachios and vanilla in a food processor and mix to combine

Add butter and pulse to form a dough

Roll dough into 1 1/2 inch balls and place on parchment lined baking sheets. Flatten tops and bake in preheated 350 oven until golden; about 15 minutes

Cool on racks

Drizzle with chocolate and add a whole pistachio to each cookie before chocolate sets