Place two tall milkshake glasses in the freezer to chill while making the shakes.
Place ice cream, cold coffee, milk, and chocolate syrup in the bowl of a blender.
Pulse to blend together ice cream. Add up to ¼ cup additional milk as needed to thin the shake.
Divide Jamocha shake evenly into two glasses.
Top with whipped cream and additional chocolate syrup, if desired.
Serve immediately.
Notes
Leftover shake can be placed in the freezer and re-blended, but this is best consumed immediately.
It's important that all of the ingredients are very cold before making the Jamocha shake. The espresso/coffee needs to be completely cooled (it’s best to refrigerate it or even stick it in the freezer after brewing until it is cold). If the coffee is still warm, it will begin melting the ice cream and change the consistency of the finished shake into a much thinner one.