Cook the Sweet Potatoes: Place peeled and cubed sweet potatoes in a large pot. Cover with water and bring to a boil. Cook until fork-tender, then drain well.
Mash and Cool Slightly: Mash the sweet potatoes until smooth. Let them cool just enough so they won’t scramble the eggs when mixed in.
Make the filling: Add eggs, sugar, heavy cream, melted butter, vanilla, salt, cinnamon, and nutmeg. Mix until smooth and well combined.
Transfer to baking dish: Pour the mixture into a greased 9x9 baking dish and smooth the top.
Make the topping: In a bowl, combine pecans, brown sugar, flour, and butter. Mix with a fork until crumbly.
Top and bake: Sprinkle the pecan topping evenly over the sweet potatoes. Bake at 350°F for 30–35 minutes, until set and the topping is golden.