In a small saucepan heat the coca-cola until boiling, then lower heat and simmer for about 15 minutes until the liquid is reduced by half. Put the reduced soda in the fridge for about 15 minutes until cool
Pre-heat the oven to 350°F.
Add the butter and chocolate chips to a large microwave safe bowl, and heat in 30 second increments until the butter and chocolate have melted, stirring every 30 seconds (it took me about 90 seconds total). Stir together until smooth.
Stir the sugar and cocoa powder into the butter mixture until combined. Add the vanilla extract, egg and coca-cola and mix together. Add the flour, baking soda and salt and mix until well combined.
Use an ice cream scoop to scoop tablespoon sized balls onto ungreased nonstick cookie sheets. Bake for 10-12 minutes, then cool completely.