Preheat oven to 250°F. Line a baking sheet with parchment paper and set aside.
Beat the egg whites in a large bowl with the cream of tartar on high until soft peaks form. Slowly add the sugar, in a steady stream, while continue to beat on high until stiff glossy peaks form. Gently fold in the pistachio butter, if using, and 3/4 of the chopped pistachios.
Using two spoons, dollop spoonfuls of the mixture onto the prepared baking sheet, about 2 inches apart. Sprinkle with a few more chopped pistachios (saving some for garnish at the end) and bake until the meringues are completely hard and come off the paper easily, about 1 hour to 1 hour 15 minutes. Remove from the oven and allow to cool completely.
Hull the strawberries and roughly chop them. Add half of them to a blender and purée until smooth. Reserve the remaining chopped berries for later.
Beat the heavy cream in a large bowl with the powdered sugar and vanilla, on high, until soft peaks form. Remove about 1 cup of the whipped cream and reserve. Crush up 3/4 of the cooled meringues and add them to the bowl with the cream along with the reserved chopped strawberries and half of the puréed strawberries. Fold until somewhat combined, it doesn't have to be perfect. Divide the mixture between 4 or 6 individual serving glasses (depending on the size of the glass). Top each with the reserved whipped cream, reserved crushed up meringues, remaining puréed strawberry and finally some more chopped pistachios. Enjoy immediately or refrigerate until ready to serve. Enjoy!