If you have leftover mashed, boiled or baked potatoes, please don’t toss them. Yes, I know, leftover potatoes are less than sexy. They’re pale and watery; they don’t reheat well. With a bit of work, however, they can make a tasty meal in a new guise.
Here’s what you do: Preheat the oven to 425. In a bowl, combine your (peeled) leftover potatoes with ½ cup to 1 cup warm milk. If you’re starting with mashed potatoes, add less milk; if you’re working with whole potatoes, add more milk and mash until you have a chunky puree. Add kosher salt and ground black pepper to taste.
Sauté some mushrooms in a bit of olive oil or butter. Add to the potatoes; mix. Butter a pie pan, add the potato-and-mushroom puree, and smooth it out with a spoon. Top with shredded cheese—what kind and how much is up to you. I used provolone and Swiss, which worked fine. Bake 20-30 minutes, until the potatoes are heated through and the top layer is golden-brown.
This is an easy, weeknight version of the potato-mushroom-and-cheese casserole (photo above) that I had in Tallinn last summer. I’ll soon make the real version, with wild mushrooms and about 20,000 calories worth of cheese and butter.