In a small saucepan, heat sugar and water. Stir until sugar has dissolved. Turn off the heat.
Whisk in cocoa powder and espresso powder. Continue to whisk until completely dissolved and few or no lumps remain. Stir in vanilla extract and Irish whiskey.
With a fine-mesh strainer, strain into a jar or bottle.
Store in the fridge for up to one month.
Irish cream cold foam
Add whipping cream, Irish cream liqueur and sugar to a medium measuring cup or small mixing bowl.
Using a milk frother or hand mixer, whip the cream until all ingredients are combined and the mixture has thickened. It does not need to be as stiff as whipped cream.
Store in an airtight, food-safe container for up to 3 days. You make need to re-whip it if it settles.
Irish cream cold brew
Add ice to a 12-ounce glass. Top with cold brew coffee, leaving about an inch at the top of the glass for the cold foam.
Stir in Irish cream simple syrup to sweeten, if desired.
Spoon Irish cream cold foam over top.
Notes
In lieu of the Irish cream liqueur in the cold foam, you can use Irish cream simple syrup instead. Be sure to omit the sugar or it will be very sweet.