Preheat & Prep: Preheat the oven to 350°F (175°C). Grease a 9×13-inch baking dish and set aside.
Cook Sweet Potatoes: Add the peeled sweet potato chunks to a large pot of salted water. Bring to a boil and cook until fork-tender, approximately 15–20 minutes. Drain well and let the potatoes steam off excess moisture for 2–3 minutes.
Mash & Mix Filling: In the pot or a large mixing bowl, mash the sweet potatoes until smooth. Stir in the melted butter, maple syrup, brown sugar, milk, beaten eggs, vanilla extract, cinnamon, nutmeg, and salt until the mixture is creamy and fully combined.
Assemble Base: Spread the sweet potato filling mixture evenly into the prepared 9×13-inch baking dish, creating an even layer.
Prepare Topping: In a medium mixing bowl, combine the chopped pecans, all-purpose flour, light brown sugar, cinnamon, and a pinch of salt. Stir in the melted butter and maple syrup until the mixture forms coarse clumps with evenly coated pecans.
Top & Bake: Sprinkle the pecan mixture evenly over the sweet potato layer, pressing lightly so it adheres properly. Bake in the preheated 350°F oven for 25–30 minutes, until the topping is golden brown and the casserole is heated through.
Optional Broiling: For extra color and crispness, broil on low for 1–2 minutes, watching closely to prevent burning.
Rest & Serve: Remove the casserole from the oven and let it rest for 10 minutes to allow it to set slightly. Serve warm alongside your favorite entrées.