a nice big glass, half-filled with crushed ice
1 - 2 tablespoon chocolate syrup, like Monin or Torani or Da Vinci (or any flavor you like, I like chocolate!)
1/2 cup milk
1/2 cup Pellegrino or Perrier or soda water
Put the ice into the glass. Add the chocolate syrup (or any flavor of syrup you like, there's a whole passel of them). Then add the milk and give it a good stir. Finally add the soda water and give it a gentle stir. Add a straw and you're good to go.