Blend the pistachios with milk to a smooth consistency.
Transfer it to a heavy bottomed pot, and simmer for 3 minutes until the raw smell of pistachios goes away.
Add the half and half, vanilla, and white chocolate. Simmer for 1-2 minutes until everything is silky and smooth
Optional cheese foam - whip the cream with powdered sugar and vanilla for two minutes to get the foam consistency.
Ladle into serving cups, top with optional cheese foam and slivered pistachio. Serve hot or warm.