Sweet Potato Casserole

To prepare the mashed sweet potatoes:
4 large sweet potatoes
Half a cup of granulated sugar
1 teaspoon kosher salt
1 teaspoon vanilla
2 large eggs
A cup of melted unsalted butter
For the streusel topping:
1 cup light brown sugar, packed
cup all-purpose flour
1 cup chopped pecans
A cup of melted unsalted butter
Cook the potatoes in the desired way until soft. Look at the notes.
Preheat oven to 375°F. Spray a 2-quart baking dish with nonstick spray (I use coconut oil spray). sit aside.
In a large bowl, combine the cooked sweet potatoes, granulated sugar, salt, vanilla, eggs, and melted butter. Beat with an electric mixer for 4-5 minutes, until fluffy and smooth.
Pour into prepared dish. Bake for 25 minutes.
While baking, make a layer of streusel by combining the brown sugar, flour, walnuts, and melted butter in a small bowl. Mix with a fork and set aside.
Sprinkle the baked sweet potato mixture with the streusel and return to the oven for 10-15 minutes, until lightly browned. Serve immediately or cover with foil and serve within 30 minutes.