How to Make It
Preheat oven to 425°F. Wash and thoroughly dry outside of sweet potatoes. Wrap in aluminum foil and place on an aluminum foil lined baking sheet. Bake for 1 1/2 hours; remove and allow to cool until you can easily remove the skins, about 30 minutes.
Preheat oven to 350°F. Grease a glass 9- x- 13-inch baking dish with cooking spray; set aside. In the bowl of a mixer or with an electric hand mixer, beat sweet potatoes on medium-high until they become smooth, about 2 minutes. Add butter, brown sugar, granulated sugar, and cinnamon; mix until fully combined. Add eggs, milk, vanilla, and salt; beat on medium high until the mixture is fully homogenous. Pour into prepared baking dish.
In a bowl, stir together brown sugar, flour, salt, and cinnamon until well combined. Add pecans and toss to coat. Add melted butter and stir until butter is evenly absorbed. Scatter across the surface of the soufflé. Bake until the center of the soufflé is set and does not jiggle when tapped, 45 to 55 minutes.