Preheat the oven to 375°F. Line a baking sheet with aluminum foil and set aside. Scrub the sweet potatoes and prick them with a fork over all sides, place them on the prepared sheet. Bake for 35 - 45 minutes or until they are fork-tender.

Slice the skin of the sweet potatoes and scoop out the flesh into a mixing bowl. You will likely find the peels easily lift away but you can also use a spoon to help.

Add the white sugar, milk, eggs, vanilla extract, and salt to the mixing bowl and mash the potatoes together.

Spread the sweet potato filling into 2 8x8-inch baking dishes or 1 9x13-inch dish and set aside.

Cut the butter into small cubes. In a medium mixing bowl, add the brown sugar, flour, and butter and mash it together with a fork. Break the pecans up into quarters and add them to the butter mixture. You may find pinching everything together with your fingers works best.

Sprinkle the butter pecan mixture over the top of the sweet potato filling.

Preheat the oven to 400°F.

Bake room-temperature sweet potato casserole for 30 minutes or until the topping is golden brown.

Wrap the dish in aluminum foil and freeze for up to 6 months. It is easiest to thaw the casserole overnight in the fridge and then bake as directed.

If you prefer to bake from frozen, keep the aluminum foil covering in place for 20 minutes, unwrap the casserole and continue to bake for another 20 - 30 minutes or until the filling is bubbling hot and the topping is golden brown.