Place the pistachios in a food processor and blend until smooth, scraping down the processor as you go. It will take about 20 minutes for the oils to release and turn into a thick paste. Be patient!
Once a paste has formed, add the salt and vanilla bean paste, blending until well combined. Transfer to a well sealed jar.
In a small bowl, gently stir together the gelatin powder and water. Let it sit for at least 5 minutes until a gel forms.
In a medium saucepan over medium-low heat, whisk together the heavy cream, milk, ½ cup (120 g) pistachio butter, and sugar until smooth. Bring to a simmer or until the edges begin to foam and bubble.
Once simmering, turn off the heat and whisk in the vanilla and gelatin until dissolved.
Divide into 6 serving glasses and cool to room temperature, about 45 minutes to 1 hour.
Place the glasses in the fridge and chill for at least 2 hours or overnight. Cover them with a layer of plastic wrap to prevent any fridge odors from affecting the taste.
When ready to serve, top with chopped pistachios and dried rose petals (optional).
