A higher quality Hershey's syrup equivalent. Best to use at room temperature.

Great in egg creams (couple tablespoons of syrup in a cup, milk to halfway, seltzer to finish it).

Ingredients Step
3/4 c. white sugar
1/4 t. kosher salt
1/2 c. water
Combine in small saucepan. Bring to boil over medium heat, whisking.
1/2 c. unsweetened cocoa powder, preferably Dutch-processed Add cocoa powder while whisking. Whisk until smooth.
1 oz. (3 T) unsweetened chocolate, chopped Remove from heat. Add the chopped chocolate and whisk until melted.
1 t. vanilla Whisk in.
Transfer to jar. Refrigerate.

Source: Genevieve Ko (NYT)