Preheat your oven to 350 degrees Fahrenheit and prep a small-medium sized casserole dish with cooking spray. I used a 9x9 inch casserole dish.
Use a mixer to whip together the cooked, mashed sweet potatoes (instructions to cook, bake, or microwave sweet potatoes in the post above), 2/3 cup granulated sugar, 1/4 teaspoon salt, 3/4 teaspoon vanilla extract, 1 egg beaten, 3 tablespoons unsalted melted butter. Mix until the potatoes are light and fluffy.
Pour the potato mixture into the prepared casserole dish and bake for 30 minutes.
Meanwhile, combine the crust ingredients in a small bowl - 2/3 cup brown sugar, 3 tablespoons all-purpose flour, 1/2 cup finely chopped pecans, 3 tablespoons melted butter and 1/2 teaspoon vanilla extract.
Sprinkle the crust over the casserole after it has baked for 30 minutes. Bake for 10-15 minutes longer, until the pecan crust is lightly browned and crunchy.