> 2 lbs Yukon Gold potatoes
> 3 tbsp butter, divided
> 1 medium leek, trimmed, washed, and thinly sliced
> 1/2 small red cabbage
> 3/4 cup whole milk
> 1 tbsp chopped chives (optional)
Peel and cut the potatoes into 2-inch chunks. To a large pot, add potatoes, salt, and enough cold water to cover by 2 inches. Partially cover and heat to a boil on high. Reduce heat and simmer 15 min., until very tender.
Meanwhile, in a 12-inch skillet, melt 1 tbsp butter on medium-high. Add the leek and sauté 4–5 min., until softened, stirring frequently. Meanwhile, very thinly slice or grate the cabbage using the large holes of a box grater, aiming for 4–5 cups. Add 1 tbsp butter to leeks in pan. Sauté, stirring occasionally, 10–12 min., until cabbage is fully softened.
When potatoes are done, drain and return to pot. Add remaining 1 tbsp butter and milk to potatoes. Season with salt and pepper. Mash with a potato masher until butter is melted and potatoes are smooth. When cabbage mixture is done, stir into mashed potato mixture. Garnish with the chives, if desired.