In a food processor add the powdered sugar, white chocolate, cocoa powder, dark chocolate, salt, vanilla bean seeds and instant coffee.
Pulse until the mixture is finely ground.
Continue pulsing until all the chocolate is finely grounded and no large pieces remain (Try not to use the processor continously so that it doesnt get warm and melt the chocolate)
Place the cocoa mix to an airtight container. The mixture will store indefinitely at room temperature.
To prepare the cocoa
Whisk 3 tablespoons (about one ounce) of cocoa mix into 6 ounces of boiling milk. Adjust with more cocoa to taste.