Boil the diced sweet potato cubes until soft. While the potatoes are boiling, butter a 9×13 baking dish and set aside. Drain and mash the potatoes in the bowl of a stand mixer (or by hand). Preheat oven to 325 F.
Beat the remaining filling ingredients (sugar, eggs, salt, butter, milk, vanilla) into the sweet potatoes, until smooth. Transfer into your prepared baking dish.
In a medium bowl, mix the brown sugar and flour. Cut the softened butter into the mixture until it’s crumbly – I find it easiest to go in with my (clean) hands for this part. Stir in the pecans. Sprinkle topping over the mashed sweet potato
Bake for 30 minutes, or until the top is lightly browned.
This is a good recipe to make with kids, because there are very straightforward “jobs” to assign – peeling the potatoes, mashing the potatoes, mixing the topping.