Preheat your oven to 375°F and line a large baking sheet with foil. Wash and poke the sweet potatoes with a fork, then roast for 35-40 minutes until completely tender. The flesh should yield immediately to a fork.
Remove potatoes from the oven and let cool for 5 minutes until safe to handle. Peel away the skin—it should slide off effortlessly once the potato cools slightly. Discard the skin and place the cooked flesh in a large mixing bowl.
Mash the roasted sweet potatoes with a potato ricer or masher until completely smooth with no lumps remaining. This step ensures the creamy buttery maple sweet potato casserole recipe achieves that signature silky texture throughout.
Add the butter, heavy cream, maple syrup, 1/4 cup brown sugar, vanilla extract, cinnamon, nutmeg, salt, and black pepper to the mashed potatoes. Stir vigorously until fully incorporated and the mixture is completely homogeneous, approximately 2 minutes.
Transfer the mixture to a buttered 9x13-inch baking dish, smoothing the top with a spatula. In a small bowl, combine the chopped pecans, 2 tbsp melted butter, 2 tbsp brown sugar, and 1/4 tsp cinnamon, then scatter evenly over the potato mixture.
Bake for 12-15 minutes until the pecan topping turns golden and fragrant, then remove from the oven. Let the buttery maple potato casserole rest for 3-4 minutes before serving, allowing the flavors to set slightly.