In a small saucepan
heat the milk
over a medium-low heat until scalding, about 4 minutes. While the milk is warming, put cocoa powder
into a mug. Add the water to the mug and stir until the mixture has the consistency of a paste. Remove the ginger from the warmed milk. Add the chocolate mixture to the milk and whisk
until slightly frothy
. Pour the hot chocolate into the mug and top with chocolate shavings.