The Irish know their potatoes. That is a fact. Sure they originated in southern Peru and were brought to most of Europe by the Spaniards in the mid 16th century, but the Irish, they saw the potential of the potato and turned it into an art form.
Champ is something that many, including my Grandfather, grew up eating. Often the only thing served for a meal, Champ was a mixture of mashed potatoes, spring onions (a.k.a. chives and green onions) milk and a lot of butter. Champ was also served with a fried egg, like Bubble and Squeak often was, and some enjoy sausages and other meats with it.