In a large bowl, sift powdered sugar.
Sift instant dry milk on top of powdered sugar.
Sift cocoa powder on top.
Whisk in granulated sugar until well combined.
Store in airtight container or jar for up to 3 months.
To make hot cocoa, add 1/3 cup of mix in a mug, stir in 1 cup warm milk, add toppings of your choice.