Roast the potatoes: Preheat the oven to 400°F (200°C). Prick the sweet potatoes with a fork and roast for 45–50 minutes until tender. Let cool slightly, then peel.
Whip the base: 1- In a large bowl, add the roasted sweet potatoes, butter, cream, brown sugar, maple syrup, egg, vanilla, cinnamon, nutmeg, and salt. 2-Whip using a hand mixer until smooth and fluffy.
Prepare the topping: In a small bowl, mix the pecans, brown sugar, melted butter, and flour until crumbly.
Assemble and bake: Spread the whipped sweet potato mixture into a small baking dish (around 8x8 inches). Sprinkle the pecan topping evenly.
Bake at 350°F (175°C) for 25–30 minutes, until golden and set.
Serve warm: Scoop into plates and enjoy your silky whipped sweet potato casserole with your favorite main dish.