Place the shelled pistachios in a high-speed blender with 1/2 cup of the whole milk. Blend on high until a very smooth, fine paste forms. This may take 3-5 minutes, scraping down the sides as needed to ensure all pistachios are pulverized.

Pour the pistachio paste into a medium saucepan. Add the remaining 1.5 cups of whole milk, heavy cream, granulated sugar, almond extract, vanilla extract, and salt. Whisk everything together until well combined.

Heat the mixture over medium-low heat, stirring constantly with a whisk, for about 5-7 minutes, until the sugar has fully dissolved and the mixture is warm but not boiling. Do not allow it to come to a boil, as this can curdle the cream. Remove from heat.

If using, stir in the green food coloring now, a drop at a time, until your desired shade of pistachio green is achieved.

Carefully pour the warm pistachio soup through a fine-mesh sieve into an airtight container. Press any solids remaining in the sieve to extract as much liquid as possible, discarding the fibrous pulp. This step ensures a silky-smooth texture.

Cover the container and refrigerate for at least 4 hours, or preferably overnight, until thoroughly chilled. The soup will thicken slightly as it cools.

Before serving, give the chilled soup a good whisk to ensure it's smooth and evenly mixed. Ladle into small serving bowls or elegant glasses.

Garnish each serving with a sprinkle of toasted chopped pistachios and a few vanilla cake crumbs. A light dusting of powdered sugar is optional for extra sweetness and presentation.