Matt Lewis and Renato Poliafito firmly believe that homemade hot chocolate is superior to any commercial mix. They make their decadent version with both bittersweet and milk chocolate and then top it with marshmallows that they make and sell at Baked.
In a medium bowl, combine the bittersweet chocolate with the milk chocolate. Add the boiling water and let stand for 1 minute. Whisk the chocolate mixture until it is smooth.
In a small saucepan, bring the milk and heavy cream just to a simmer. Add the chocolate mixture and whisk over moderate heat until hot. Remove the saucepan from the heat and add the whiskey. Pour the hot chocolate into demitasse cups or small mugs, garnish with marshmallows and serve.