In a cup or small bowl, add a scoop or two of ice cream.
Pour the hot espresso over the ice cream and serve.
Notes
I like to freeze ice cream in these small milk glasses I thrifted. I have a set of four and I will freeze the ice cream so it goes up the sides of the glass and leaves a hole in the center for the espresso shot to be added. I keep these in my freezer so I can make an affogato anytime I want. You could also make these cups ahead for a dinner party and then all you need to do is add the espresso shots, and I make them to serve.
Use a flavored ice cream for an upgrade! I like mint chocolate chip, but cookie dough sounds pretty good too.
Instead of ice cream you could use gelato, sorbet, or frozen custard. Anything that pairs well with espresso (or dark chocolate) will be delicious.
Add toppings like you could a sundae for a nontraditional twist: sprinkles, caramel syrup, sea salt, crushed Oreo cookies, etc.
Add a shot of liquor, like amaretto, to this dessert to make it 'naughty.'