Dump all ingredients into a food processor and pulse until white chocolate chips are finely ground. This makes a large batch, so if your food processor isn't large enough, you may want to do this in two batches. Spoon mixture into an airtight container.
To make a cup of hot cocoa, measure 1/3 cup of hot cocoa mix into a large mug and pour 1 cup of hot milk on top. Stir until everything is completely combined and top with marshmallows or whipped cream if you desire.
Homemade Hot Cocoa Mix will keep for up to 3 months stored in an airtight container.