Espresso cups refers to small cups that are specifically designed for serving espresso, which is a strong and concentrated form of coffee. Full definition
Very tasty and since I wanted to serve that day, I let it set up in espresso cups. (epicurious.com)
I added some chili powder to mine to give it more complexity, and served it chilled (it was in the fridge for hours) in individual espresso cups. (epicurious.com)
Once you have achieved a mousse - like consistency, divide your chocolate into espresso cups. (thebettyrocker.com)