Preheat the oven to 375°F. Lightly grease a 9×13-inch baking dish with butter or nonstick cooking spray.
In a large mixing bowl, combine the mashed sweet potatoes, granulated sugar, beaten eggs, salt, vanilla extract, and melted butter. Beat for 2–3 minutes, or until the mixture is smooth and well combined.
Spread the sweet potato mixture evenly into the prepared baking dish.
In a separate bowl, stir together the brown sugar, flour, chopped pecans, melted butter, and vanilla extract until the mixture is evenly moistened and crumbly.
Sprinkle the pecan topping evenly over the sweet potato mixture.
Bake for 30 minutes, or until the casserole is heated through and the topping is golden brown.
Let the casserole rest for 5–10 minutes before serving warm.
Notes
Use canned sweet potatoes packed in water or syrup, and drain them well before mashing to prevent a watery casserole.
Mix the filling until smooth, but don't overbeat it once the eggs are added.
Chop the pecans into small, even pieces so every bite gets a little crunch.
Make it a day ahead, then refrigerate and bake just before serving for an easy holiday side.
Let the casserole rest for 5–10 minutes after baking so the filling sets and serves neatly.