How to Make It
In a food processor, combine the 3/4 cup of the pistachios with 1/4 cup plus 2 tablespoons of the sugar, 1 teaspoon of the salt and 2 tablespoons of water. Pulse until a smooth paste forms.
In a medium saucepan, combine the pistachio paste with the milk and bring to a simmer over moderate heat, about 12 minutes.
Meanwhile, in a medium bowl, whisk the remaining 1/2 cup of sugar with the egg yolks, cornstarch and the remaining 1/4 teaspoon of salt. Ladle about 1/2 cup of the warm pistachio mixture into the bowl and whisk until smooth. Using a heatproof spatula, scrape this mixture back into the saucepan and cook over moderately low heat, stirring constantly, until thickened and bubbling, about 5 minutes. Cook 1 minute longer. Remove the pan from the heat and stir in the butter and vanilla. Strain the warm pudding through a fine sieve into large bowl.
Press a piece of plastic wrap directly on the surface of the pudding. Refrigerate until chilled but not completely set, about 3 hours. Remove the plastic wrap from the pudding. Fold in the mini marshmallows and crushed pineapple until just combined. Scrape the pudding into a serving bowl or individual dishes. Press the plastic wrap back on the surface of the pudding and chill until set, about 1 hour. Garnish with whipped cream and chopped pistachios and serve.