1 cup water
1/2 cup sugar
2/3 cup unsweetened cocoa powder, preferably Dutch-process
1/4 teaspoon salt
1 teaspoon vanilla
Bring water and sugar to a boil, whisking until sugar is dissolved. Whisk in cocoa and salt and simmer, whisking, until slightly thickened, about 3 minutes. Remove from heat and add vanilla, then cool (syrup will continue to thicken as it cools).
**Thanks to Andrea Howard for this recipe**