Add the hazelnut syrup to the bottom of your 16-ounce cup or mug.
Brew espresso, then pour on top of the syrup and give a slight swirl to mix.
For Hot: While espresso is brewing heat the milk to 155-160° F, then froth. Pour the frothed milk over espresso and syrup almost to the top. Add milk foam to the top of the cup.
For Iced: Add cold milk over the espresso and syrup, leaving an inch or two for ice. Add ice to the top of the cup.