Our friends at Man Made Daily provide an easy-to-make dark chocolate ice cube recipe for your iced coffee. Sure, you could also enjoy them with plain cold milk but why would you do something crazy like that?
1/4 cup cocoa powder
2 cups water
1/4 cup agave syrup
Place all ingredients in a heavy-bottom pan and whisk until combined. Bring to a simmer and remove from heat
Let mix cool completely and place in ice cube trays