Preheat your oven to 350°F (175°C) and butter a 9x13-inch baking dish.

Peel and cut the sweet potatoes into large chunks, then boil until tender, about 20 minutes.

Drain the sweet potatoes and mash them until smooth with melted butter, brown sugar, milk, eggs, vanilla, salt, and cinnamon.

Spread the creamy sweet potato mixture evenly into the baking dish.

For the topping, combine chopped pecans, flour, and brown sugar, then mix in melted butter until crumbly.

Sprinkle the pecan topping over the sweet potato mixture in the baking dish.

Bake uncovered for 30-35 minutes until the topping is golden brown.

Let the casserole rest for 10 minutes before serving to allow the flavors to set.