Add all the Thandai Powder ingredients to a bowl and give a good mix. If using a small spice grinder, grind the nut mix to a fine powder in 2 to 3 batches. You can also grind it all at once in a bigger blender. Make sure not to overgrind as the nuts will start to release oils.
Store in an airtight container. Makes 2 cups of Thandai powder.
Thandai Drink
To make the Thandai, add ice, milk, sugar, rose essence and Thandai Masala to a blender jar. Blend well until smooth.
Strain the thandai if you like. Refrigerate and serve chilled. Garnish with sliced pistachios and rose petals.