In short, this is the Irish version of Vichysoisse but more designed for an 18th-century cottier rather than the 20th-century Ritz-Carlton Hotel.

Boil potatoes with salt for approximately 15 minutes or, if with the wonders of modern technology, use a potato bag and a microwave. Add milk and mash. Whilst this is happening, add butter to a pan and add Savoy cabbage, salt, pepper, garlic, and leeks until everything is tender. Combine the two dishes and stir.

When serving, include a well in the middle for a generous serving of butter and sprinkle with chives.

Ingredients
500g potato, including skins. Ignore suggestions that they should be peeled, such people don't know how to be a peasant and they don't understand nutrition
1 leek (white and light green parts, save the rest for a delicious leek soup)
2 cups finely-shredded savoy cabbage
2 tablespoons of minced garlic
2 cups of milk
Salt and black pepper, butter, chives

Go on, add pesto on St Patrick's Day. You know you want to.