Blanch the pistachios: Bring a small pot of water to boil. Add pistachios and boil for 1 minute. Immediately transfer to an ice bath to stop cooking. Once cooled, pinch off the skins and discard. Pat pistachios completely dry with a towel.

Make pistachio paste: Add the blanched, dried pistachios and 2 tablespoons of sugar to a food processor. Process for 2-3 minutes, scraping down the sides as needed, until you get a fine, smooth, oily paste. The mixture should be fragrant and well-combined.

Blend everything together: Add the pistachio paste to a blender along with vanilla ice cream, whole milk, almond extract, and a pinch of salt. Blend on medium-high speed for 45-60 seconds until completely smooth and creamy.

Check consistency: The shake should be thick but drinkable through a straw. If too thick, add milk 1 tablespoon at a time and blend again. If too thin, add a small scoop of ice cream.

Taste and adjust: Taste your shake before serving. Since cold dulls sweetness, the flavor should be bold. Add more sugar if needed, or a tiny pinch more salt to enhance the pistachio flavor.

Serve: Pour into pre-chilled glasses (place in freezer for 15 minutes beforehand). Top with whipped cream and a sprinkle of chopped pistachios if desired. Serve immediately with a thick straw.