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

Peel and cube sweet potatoes, then boil in water for about 20 minutes or until fork-tender.

Mash the sweet potatoes in a large bowl. Mix in melted butter, brown sugar, milk, eggs, vanilla extract, salt, and cinnamon.

Pour the sweet potato mixture into the prepared baking dish.

In a bowl, combine chopped pecans, extra brown sugar, and flour. Add melted butter and mix until crumbly.

Spread the pecan mixture over the sweet potato layer and bake uncovered for 30–35 minutes.

Remove from oven and let rest for about 10 minutes before serving.