• In a nonstick skillet, heat the olive oil over medium heat. Add the chopped leeks and ½ teaspoon of salt. Cook for about 10 minutes, stirring occasionally, until the leeks are tender and have taken some color. Add the thyme leaves to the leeks and reduce the heat to medium low. Cook 10 minutes longer, stirring occasionally, until they are nicely caramelized (keep a close eye on them toward the end so they don’t burn). Add a splash of water to the pan and stir to deglaze. Set the leeks aside.
• Meanwhile, while the leeks are caramelizing, add the cubed potatoes to a pot of cold water and bring to a boil. Add a large pinch of salt and boil until the potatoes are very tender, about 15-20 minutes.
• Heat the half-and-half in a small saucepan until barely simmering.
• Drain the potatoes and add them back to the pot. Add the butter and 1 cup of the hot half-and-half to the potatoes and mash to the desired level of smoothness (we like these a little chunky/rustic). Add more of the half-and half until you reach your desired texture.
• Stir in the leeks. Taste and season with additional salt and pepper to taste.

Preparing ahead

• If preparing ahead, transfer to a greased baking dish, cover and refrigerate until ready to serve (up to 2 days).
• Preheat the oven to 350F. Cut two tablespoons of butter into small pieces and sprinkle on top of the potatoes. Cover the baking dish and bake until hot all the way through, about 15-20 minutes.