Colcannon is a traditional Irish dish with mashed potatoes and greens such as kale or cabbage. This version, Irish Colcannon with Cabbage and Leeks, gets a flavor infusion from aromatics (leeks and garlic) and sour cream for tangy creaminess. Eat it as a delicious side dish, or as a topping for shepherd’s pie or lamb stew.
Fill a 7–8 qt. pot 3/4 of the way with water and bring to a boil. Add the potatoes and boil gently until a knife slips in and out of the potato pieces without any resistance (15–20 min).
Meanwhile, heat the olive oil in a skillet over medium heat. Add the leeks; sauté until softened, but not brown. Add the garlic. Sauté an additional minute. Add the cabbage; stir to combine. Lid the skillet and reduce heat to medium-low, stirring occasionally, until the cabbage is soft. Remove from heat.
When the potatoes are soft, drain well and return to the pot. Add the butter and stir to combine. After the butter has melted, add the sour cream and milk. Mash to desired consistency with a potato masher (don't worry about getting every lump out: you won't notice them with the cabbage). Add the cabbage and leek mixture along with salt and pepper. Mix well and taste for seasoning, adjusting as necessary.
Garnish with sliced scallions and chopped parsley. Serve.