A photo like it (a cortado with a medialuna) · Natalie HG (CC BY 2.0) via Wikimedia Commons · source
Spain's mid-morning coffee, and Buenos Aires' café order: a shot 'cut' with an equal splash of warm, barely foamed milk, served in a small glass so you can see the line.
18 g espresso beans for a double (or 9 g for a single, as in Madrid bars)
60 ml (1/4 cup) whole milk
A small glass or cup, about 120 ml
How to make it
Shot (30 sec): Pull the espresso into the warm glass.
Milk (15 sec): Steam the milk with only a breath of air, a second or two of stretching, then spin it to about 55 to 60°C: warm and silky, not foamy.
Cut (5 sec): Pour the milk straight into the middle of the shot until the glass holds about equal coffee and milk. A thin layer of foam on top is right.
Serve: With a small biscuit, or in Buenos Aires with medialunas, two of them.
Tips
In Madrid, ask for a 'cortado' and you'll get this; a 'café con leche' is the bigger, milkier breakfast cup.
In Buenos Aires, a 'cortado en jarrito' comes in a small mug and a 'lágrima' is the opposite: milk with a 'tear' of coffee.
Leche y leche (Canary Islands): pour a spoon of condensed milk into the glass first, then the shot, then the milk.