📖 Instructions

1. Prepare the Sweet Potatoes: First things first, grab your sweet potatoes. Give 'em a good scrub under cold running water to get rid of any dirt. Now, peel them using a vegetable peeler. You want them completely peeled, no skin left behind. Once peeled, chop them into roughly 1-inch (2.5 cm) cubes. Try to make them fairly uniform in size so they cook evenly.
2. Boil the Sweet Potatoes: Place your cubed sweet potatoes into a large pot. Cover them with cold water, making sure the water level is about an inch (2.5 cm) above the potatoes. Add a generous pinch of salt to the water – this helps season the potatoes from the inside out. Bring the water to a rolling boil over high heat, then reduce the heat to medium-low and let them simmer. Cook the sweet potatoes for about 15-20 minutes, or until they are fork-tender. You should be able to easily pierce them with a fork.
3. Drain and Mash: Once tender, carefully drain the sweet potatoes into a colander. Let them sit in the colander for a minute or two to allow any excess water to steam off. This step is super important, as too much water can make your casserole watery. Return the drained sweet potatoes to the now-empty pot.
4. Create the Creamy Base: Add the unsalted butter, light brown sugar, whole milk (or heavy cream for extra richness!), vanilla extract, ground cinnamon, ground nutmeg, and another small pinch of salt to the pot with the potatoes. Using a sturdy potato masher, mash until smooth and creamy. Some folks like a few small lumps for texture, and that's perfectly fine! Taste it and adjust seasonings if you think it needs a bit more sweetness or spice.
5. Preheat Oven and Prep Dish: While your potatoes are still warm, preheat your oven to 375°F (190°C). Lightly grease a 9x13 inch (23x33 cm) baking dish with butter or cooking spray. This helps prevent sticking and makes cleanup easier later.
6. Transfer to Baking Dish: Spoon the mashed sweet potato mixture evenly into the prepared baking dish. Smooth the top with the back of your spoon or a spatula.
7. Add the Marshmallow Topping: Now for the fun part! Arrange your large marshmallows (or miniature ones, if you're using those) in a single layer over the entire surface of the sweet potato mixture. Don't be shy; you want a nice, fluffy blanket!
8. Bake the Casserole: Place the baking dish into your preheated oven. Bake for 25-30 minutes. You're looking for the sweet potato base to be heated through and the marshmallows to be beautifully puffed up and golden brown. Keep a close eye on the marshmallows during the last 5-10 minutes, as they can go from perfectly toasted to burnt in a flash! If they're browning too quickly, you can cover the dish loosely with aluminum foil.
9. Serve and Enjoy: Once the marshmallows are perfectly golden and the casserole is bubbly, remove it from the oven using oven mitts. Let it cool for about 5-10 minutes before serving. This cooling time allows the casserole to set slightly and makes it easier to serve. Dig in and savor that sweet, creamy, gooey goodness!