Iced Chocolate Soda

Directions

1. 1.

   Heat milk, cocoa powder, sugar, and vanilla in a small saucepan over medium, stirring occasionally, until mixture comes to a rapid simmer, about 3 minutes. Remove from heat and whisk in chocolate until melted and smooth. Let cool slightly, about 5 minutes.

2. 2.

   Transfer mixture to a cocktail shaker. Fill shaker with ice, cover, and shake vigorously until outside of shaker is very cold, about 20 seconds. Strain into a tall, thin glass filled with ice. Top with sparkling water, stir once, and serve.