01 - Preheat the oven to 350°F. Lightly grease a 9x13-inch baking dish with butter or non-stick spray.
02 - Place sweet potato cubes in a large saucepan, cover with cold water, and bring to a boil. Simmer until fork-tender, about 12 to 15 minutes. Drain thoroughly.
03 - Transfer cooked sweet potatoes to a large bowl. Mash until smooth. Incorporate melted butter, maple syrup, milk, eggs, vanilla extract, cinnamon, nutmeg, and salt, mixing until a creamy, uniform mixture forms.
04 - Spread the sweet potato mixture evenly across the prepared baking dish.
05 - In a separate bowl, combine flour, brown sugar, melted butter, pecans, maple syrup, cinnamon, and a pinch of salt. Mix ingredients together until a crumbly topping forms.
06 - Sprinkle the pecan topping evenly over the sweet potato layer.
07 - Bake for 35 to 40 minutes until the topping is golden and the filling is set. Allow the casserole to cool for 10 minutes before serving.