Black coffee is poured into the mug. Whiskey and at least one level teaspoon of sugar is stirred in until fully dissolved. The sugar is essential for floating liquid cream on top.Thick cream is carefully poured over the back of a spoon initially held just above the surface of the coffee and gradually raised a little. The layer of cream will float on the coffee without mixing. The coffee is drunk through the layer of cream.
To ensure the integrity of the ingredients of Irish Coffee, NSAI, Ireland’s national standards body, published an Irish Standard, I.S. 417 Irish Coffee, in 1988.