In a bowl combine the cocoa powder and boiling water.
Bring the sugar and water to a simmer in a small saucepan. Stirring until sugar is dissolved.
Add the sugar syrup to the cocoa syrup to a mason jar or whatever you want to use to infuse while in the fridge. Add the vodka, cover and refrigerate for 7 days.
To use stir or shake well before straining into your bottle. I found I did not need to strain before funneling into my flip top bottle.
Make sure to shake really well to redistribute the chocolate