Begin by brewing a shot of espresso. If you have an espresso machine, ensure that your equipment is clean, and the coffee grounds are fresh and finely ground.
Take the milk and pour it into a pitcher or a small metal container suitable for frothing. Heat the milk to around 140°F (60°C).
Once heated, froth the milk using a milk frother or a steam wand until you achieve a velvety microfoam texture.
Gently pour the freshly brewed espresso into your cup, filling it up to about 1/3 or 1/2 of the cup. The remaining space will be filled with milk.
Last, carefully pour the frothed milk into the cup, allowing it to mix with the espresso. The milk should be warmed but not too hot, and the microfoam will create a smooth, creamy texture on top of the espresso.
Notes
While whole milk is best for its foaming properties, you can use a different percentage of dairy milk or a milk alternative if needed.
If you want to sweeten your cortado, I would recommend simple syrup or honey.