In a medium saucepan, combine the water with the cup of cocoa powder (sifted for a smoother texture). Whisk them together until the cocoa is fully dissolved and the mixture is smooth.
Add your granulated sweetener and ⅛ teaspoon of salt to the wet cocoa mixture, stirring continuously over medium heat. Ensure that the sugar is completely dissolved and the mixture is smooth, being careful not to let it boil over, before you let it simmer.
Once the mixture is fully combined and comes to a gentle boil, reduce the heat to low and let it simmer for about 5 minutes. If not using a nonstick pot, keep stirring occasionally to prevent the syrup from burning at the bottom of the pan.
Remove the saucepan from the heat. Stir in the ¼ teaspoon of vanilla extract to add a layer of flavor to your homemade chocolate syrup. Along with the salt, the vanilla will also help to enhance the overall chocolate taste.
Allow the chocolate syrup to cool for a few minutes in the pan. It will thicken as it cools. Once the syrup has cooled down enough to handle, pour it into a glass jar or a bottle using a funnel. If you find the syrup is too thick, you can stir in a little extra water, a tablespoon at a time, until you reach your desired consistency.