Using a food processor, process the pistachios and milk powder until you have a fine powder that is slightly moist.Stop the mixing 2-3 times and use a rubber spatula to scrape the sides of the bowl.
Mix in the oil and process until it is fully incorporated.
Process the powdered sugar, and process until incorporated. The longer you process, the thinner the cream will turn.
Use or transfer to an airtight container and refrigerate.
Notes
Refrigerate for up to ten days in an air-tight container.
Roasting the pistachios before blending brings out their natural oils and enhances the flavor; however, using raw pistachios is ok.
Add flavoring: You can enhance the flavor and add another layer of flavor by adding 1/2 teaspoon of almond extract, vanilla bean paste, or vanilla extract.
The longer you process the cream, the thinner it will be. Use vegetable shortening instead of oil for a thicker cream with a peanut butter consistency, or mix in 1/2 cup of melted white chocolate. (adding white melted chocolate will alter the recipe to a close version of Italian Pistachio cream or crema al pistacchio)