Combine the cocoa powder, sugar, salt, water, and vanilla in a medium saucepan.

Put the saucepan over medium heat. Whisk constantly until the mixture thickens and begins to boil

Remove the pan from the heat. It will thicken as it cools so don't worry if it seems thin.

Let the syrup cool before storing it in an airtight jar.

Makes two cups of syrup.