Preheat the oven to 400°F (200°C).

Bake the sweet potatoes: Pierce them with a fork and place them on a lined baking sheet. Bake for 45–50 minutes, or until fork-tender.

Mash until smooth: Once cooled, remove the skins and mash until creamy. Use a potato masher or hand mixer for a smoother consistency.

Lower the oven temperature to 350°F (175°C).

Combine ingredients: In a large bowl, mix together the mashed sweet potatoes, granulated sugar, melted butter, heavy cream, eggs, vanilla extract, and salt until smooth.

Transfer to a baking dish: Lightly grease a 9x13-inch baking dish and spread the sweet potato mixture evenly.

Mix the streusel topping: In a separate bowl, combine the brown sugar, flour, softened butter, and chopped pecans. Use a fork or your hands to create a crumbly texture.

Sprinkle over the casserole: Evenly distribute the pecan streusel topping across the sweet potato filling.

Bake uncovered for 30–35 minutes, or until the topping is golden brown and crisp.

Let it rest: Allow the casserole to cool for 5–10 minutes before serving.