Place the pistachio butter and the chopped pistachios in two separated small plates. Dip the glass first in the pistachio butter, making sure the outer top side is covered with a thick layer. Roll the top of the glass in the chopped pistachios and cover evenly.
Use a hand mixer or a stand mixer, and whip the heavy cream, sugar, and vanilla extract on medium-high speed until you see peaks starting to form, it will take 3 to 4 minutes.
Combine all the shake ingredients in a food processor, process until smooth and then transfer to the glass.
Fill the piping bag with whipped cream and pipe onto the top of the glass to create the frosting. Stick a straw and serve!