Prepare the White Hot Cocoa: In a medium saucepan over low to medium heat, combine the milk, white chocolate, vanilla extract, and a pinch of salt. Stir constantly until the chocolate is fully melted and the mixture is smooth and hot, but avoid boiling. Set aside.
Make the Matcha: Add warm water into a mixing bowl. Sift the matcha powder on top to avoid clumps. Whisk all together until smooth and frothy, using a bamboo whisk or small electric whisk in an M or W motion.
Assemble: Pour the white hot cocoa into serving cups, filling each about two-thirds of the way. Add a matcha shot on top, gently stirring to create a beautiful swirl.
Top with Cream Foam or Marshmallows (Optional): For the cream foam, whisk heavy cream with a splash of milk, vanilla extract, and sugar until thick but not stiff; avoid overwhipping. Spoon a dollop of this soft foam over each drink and sift matcha powder on top. Alternatively, top with mini marshmallows and carefully toast them with a kitchen torch until golden brown for a toasty finish.