Leeks can be hard to clean, but they're worth the effort for their sweet, subtle yet unmistakable flavor. Cooked until very tender, they blend beautifully with mashed potatoes.
Serves 10 to 12
1. Cook leeks: Melt 2 tbsp. butter in a large frying pan over medium heat. Add leeks, 1/2 tsp. salt, and the pepper. Cook until leeks are very soft and separated into rings, stirring occasionally, 12 to 15 minutes. Add water if needed to keep from scorching, 2 tbsp. at a time. Set aside.
2. Put potatoes in a large pot and add enough cold water to barely cover. Stir in 1 tsp. salt. Bring to a boil over high heat, covered. Reduce heat to medium and boil gently until potatoes are tender when pierced, about 15 minutes. Drain; return to pot, off the heat.
3. Mash hot potatoes with a potato masher until all large chunks are broken and potatoes are fluffy. Add milk, 2 tbsp. butter, and 1 1/2 tsp. salt and mash to blend. If leeks are cool, gently warm in microwave. Stir all but 1/2 cup of leeks into potatoes.
4. Transfer to a serving bowl and scatter remaining leeks over the top.
Make ahead: Leeks, up to 5 days, chilled. Mashed potatoes, up to 1 day, chilled; reheat in a microwave until hot (if they've stiffened up, add enough milk to make them creamy).