Preheat your oven to 375°F (190°C). Grease a 9x13 inch baking dish with butter.
In a large pot, bring water to a boil. Add the sweet potato cubes and cook for 15-20 minutes, or until fork-tender.
Drain the sweet potatoes and return them to the pot. Mash them while they're still hot.
Add the melted butter, maple syrup, milk, beaten eggs, vanilla extract, cinnamon, nutmeg, and salt to the mashed sweet potatoes. Mix well until everything is thoroughly combined.
Transfer the sweet potato mixture to your prepared baking dish, spreading it out evenly.
In a separate bowl, mix together all the ingredients for the pecan topping until well combined.
Sprinkle the pecan topping evenly over the sweet potato mixture.
Bake for 25-30 minutes, or until the topping is golden brown and crispy.
Let it cool for 5-10 minutes before serving.