📖 Instructions

1. **Prep the Sweet Potatoes:** First things first, get those sweet potatoes ready. Peel approximately 3 pounds of sweet potatoes (about 4-5 medium ones). Cut them into roughly 1-inch chunks. This helps them cook evenly and faster. Place the cut sweet potatoes in a large pot and cover them with cold water by about an inch. Add a pinch of salt to the water; it brings out the natural sweetness.
2. **Boil and Soften:** Bring the pot to a rolling boil over high heat. Once boiling, reduce the heat to medium-low, cover, and let them simmer for about 15-20 minutes, or until the sweet potatoes are fork-tender. You should be able to easily pierce them with a fork. Don't overcook them to mush, but make sure there’s no resistance. Drain the sweet potatoes thoroughly in a colander, letting any excess water steam off for a few minutes. This is crucial for a non-watery casserole.
3. **Mash the Sweet Potatoes:** Transfer the drained sweet potatoes to a large mixing bowl. Add 1/2 cup (1 stick) of unsalted butter, softened, 1/2 cup packed light brown sugar, 1/4 cup whole milk (or heavy cream for an extra rich texture), 1 teaspoon pure vanilla extract, and 1/2 teaspoon ground cinnamon. Using an electric mixer on medium speed, or a sturdy potato masher, mash and whip the sweet potatoes until they are completely smooth and creamy. Make sure there are no lumps! Taste and adjust sweetness or spice if needed. This is where your personal touch comes in – if you like it sweeter, add a little more brown sugar, a tablespoon at a time.
4. **Add the Eggs:** Once the sweet potato mixture is smooth and slightly cooled (so you don't scramble the eggs), crack in 2 large eggs. Mix them in with the electric mixer on low speed, just until they are fully incorporated. The eggs help bind the casserole and give it a lovely, almost custardy texture.
5. **Prepare the Baking Dish:** Lightly grease a 9x13 inch baking dish with butter or cooking spray. Pour the whipped sweet potato mixture into the prepared dish and spread it evenly with a spatula. At this point, you can cover and refrigerate it overnight if you're making it ahead of time. Just let it come to room temperature for about 30 minutes before baking.
6. **Make the Pecan Streusel Topping:** In a separate medium-sized bowl, combine 1 cup chopped pecans, 1/2 cup packed light brown sugar, 1/4 cup all-purpose flour, and 1/4 teaspoon ground cinnamon. Add 1/4 cup (1/2 stick) of cold unsalted butter, cut into small cubes. Use your fingertips, a pastry blender, or two knives to cut the butter into the dry ingredients until the mixture resembles coarse crumbs. Don't overmix; you want some nice crumbly bits!
7. **Assemble and Bake:** Preheat your oven to 375°F (190°C). Evenly sprinkle the pecan streusel topping over the sweet potato mixture in the baking dish. Don't be shy; cover it generously. Place the baking dish on a baking sheet to catch any potential drips (though with this recipe, it's unlikely).
8. **Bake to Perfection:** Bake for 30-35 minutes, or until the sweet potato casserole is heated through, slightly puffed, and the streusel topping is golden brown and bubbly. If the topping starts to brown too quickly, you can loosely tent it with aluminum foil. Remove from the oven and let it rest for 5-10 minutes before serving. This allows it to set slightly, making it easier to serve. Enjoy your heavenly creation!
9. **Optional Marshmallow Layer:** If you're a fan of marshmallows, you can add a layer! Instead of or in addition to the pecan streusel, sprinkle about 2-3 cups of mini marshmallows over the casserole during the last 10 minutes of baking. Watch carefully, as they brown very quickly! For a combination, you can add the pecan streusel for the full bake time, then add marshmallows for the last 5-7 minutes. It's truly delicious either way!