Preheat oven to 375°F. Lightly grease a 9x13-inch baking dish with nonstick spray or butter.
Place the sweet potatoes in a large pot and fill it with enough water to cover the potatoes by 1 inch. Bring to a boil over high heat and cook until very tender, about 15 to 20 minutes. Drain well.
Transfer the sweet potatoes to a large bowl and mash with a potato masher or large fork. Add the eggs, melted butter, brown sugar, vanilla, salt, and cinnamon to the mashed sweet potatoes, then beat with an electric mixer or stir with a wooden spoon until well combined. (A hand mixer will result in a smoother filling.) Fold in ½ cup of the toasted pecans.
Spread the sweet potato mixture into the greased baking dish and smooth into an even layer. Top with the mini marshmallows and remaining chopped pecans.
Bake for 25 minutes or until the marshmallows are golden.
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Notes
Opt for small to medium-sized sweet potatoes. They are sweeter and less watery than the very large ones. When mashed, they will be creamy instead of runny.
Use walnuts. You can use walnuts instead of pecans, or combine them! Both nuts pair very well with sweet potatoes.
Add candied pecans. If you want the casserole to be more on the dessert end of the spectrum, use candied pecans.
Add more pecans. For added crunch, feel free to add more toasted pecans to the sweet potato mixture!
Add bourbon. It seems like an unlikely pairing, but smoky bourbon adds depth to the mashed sweet potatoes. Add 2 to 3 tablespoons of bourbon to the sweet potatoes along with the eggs.
Skip the marshmallows. If you aren’t a marshmallow fan, just leave them out!