01 - Whisk together sugar, cocoa powder, and salt in a medium saucepan until fully blended.
02 - Add water and whisk the mixture until smooth.
03 - Place the saucepan over medium heat and stir constantly until the mixture reaches a gentle boil.
04 - Reduce heat and simmer for 3 to 4 minutes, stirring continuously until the syrup slightly thickens.
05 - Remove from heat and stir in vanilla extract.
06 - Let the syrup cool to thicken further, then transfer to a clean jar or bottle and refrigerate for up to 2 weeks.