Random internet recipe.

INGREDIENTS

5 medium Yukon Gold potatoes (about 1¾ pounds), peeled and roughly chopped
Kosher salt
6 tablespoons unsalted butter, divided
2 leeks, white and pale-green parts only, sliced in half lengthwise, thinly sliced crosswise
2 garlic cloves, thinly sliced
2 cups (packed) shredded savoy cabbage (from about ¼ large head), divided
1¼ cups milk
½ cup heavy cream
Salt and Pepper

METHOD

Cover the potatoes with water in a stock pot and season with salt.
Bring to a boil over medium-high heat, then reduce heat and simmer until easily pierced with a fork, 15 – 20 minutes.

Meanwhile, melt 4 tablespoons of butter in a large saucepan over medium-heat.
Add the leeks and cook, stirring frequently, until very soft, about 8–10 minutes.
Add the garlic and cook, stirring frequently, until garlic is fragrant and leeks are just beginning to brown around the edges, about 3 minutes longer.

Add 1 cup cabbage and cook, stirring constantly, until wilted.
Add the milk and cream and bring to a simmer.
Add potatoes and remaining 1 cup cabbage, then coarsely mash with a potato masher.
Season to taste with salt and pepper.