Preheat your oven to 425°F (220°C). Scrub sweet potatoes, prick them with a fork, and bake for 40 to 50 minutes until tender.

Once baked, cool for 15 minutes, then peel the sweet potatoes.

In a large bowl, mash sweet potatoes and mix in milk, eggs, sugar, melted butter, salt, vanilla, and cinnamon until smooth.

Grease a 9×13 baking dish and pour the sweet potato mixture into it, spreading evenly.

In another bowl, combine brown sugar, flour, and pecans. Cut in softened butter until crumbly.

Sprinkle the streusel mixture over the sweet potato layer in the dish.

Bake the casserole for 40 to 45 minutes, until the filling is set and topping is golden brown.

Let cool for 10 minutes before serving warm.