Make the cocoa whipped cream:
In a small bowl, mix the cocoa and confectioners' sugar. In a chilled bowl, combine the cream and vanilla and whip until soft peaks form. With the mixer running or while whisking by hand, gradually pour in the cocoa mixture; whip until well blended.
Make the hot chocolate:
Bring the milk just to a boil. Put the white chocolate in a blender and pour in the hot milk. Let sit for 10 to 15 seconds so the chocolate begins to melt and then cover securely, place a folded towel over the lid, and blend until completely mixed and froth, about 30 seconds. Pour into mugs and top with the cocoa whipped cream.
Photo: Scott Phillips