This recipe from Stephen Bruce, Serendipity 3, New York, New York.

Montezuma, emperor of the Aztecs, poured his liquid chocolate over bowls of snow from nearby mountaintops before whipping the mixture into a chilled froth. Five centuries later, a trio of adventurous New York City restaurateurs concocted an icy, wickedly rich confection, keeping its formula a well-guarded secret and thus guaranteeing a faithful following for the legendary dessert. Stephen Bruce, who founded Serendipity 3 with two partners in 1954, was badgered and begged for his recipe, but for decades he refused to budge - not even for the first lady Jackie Kennedy, who wanted to serve the dessert at a White House function. On the occasion of Serendipity's fiftieth anniversary, however, he finally spilled the beans. Frozen Hot Chocolate, it turns out, gets its complex flavor from a dozen different cocoas that are blended with crushed ice to the consistency of a frozen daiquiri. While an authentic reproduction would call for assembling 1/2 ounce of all twelve cocoas, this version is a little more user-friendly. Whether sipped through a straw or eaten with a spoon, it's a sweet invitation to childhood.

Ganache:
3 ounces unsweetened cocoa
3 ounces sweetened cocoa
1 1/2 tablespoons sugar
1 tablespoon unsalted butter
1/2 cup whole milk

Hot Chocolate:
1 cup whole milk
2 cups crushed ice
basic whipped cream
chocolate shavings for serving

Makes 1 Large Serving

To make the ganache, in the top of a double boiler over boiling water, combine the cocoas, sugar, and butter and melt until it forms a smooth paste. Slowly drizzle the milk into the chocolate mixture, stirring constantly until thoroughly blended and smooth as silk. Cool to room temperature.

To make the drink, combine 1/2 cup of the ganache with the milk and crushed ice in a blender and blend on high speed until the mixture if the consistency of a frozen daiquiri. Pour into a large goblet, top with a mound of whipped cream, and sprinkle with chocolate shavings. Serve with 2 straws for sipping and an iced tea spoon for devouring.