Preheat your oven to 350°F.
Grease a medium-sized baking dish with cooking spray or butter to prevent sticking.
In a large bowl, mix together the mashed sweet potatoes, sugar, 1/2 cup of softened butter, beaten eggs, vanilla extract, and whole milk.
Stir until the mixture is well combined and smooth.
Pour the sweet potato mixture into your prepared baking dish.
Spread it evenly to ensure a consistent bake.
In a separate bowl, combine the brown sugar, flour, chopped pecans, and melted 1/3 cup butter.
Mix with a fork until the mixture forms coarse crumbs.
Sprinkle this crumb mixture evenly over the sweet potato mixture in the baking dish.
Bake in the preheated oven for about 30 minutes.
The topping should be golden brown and the sweet potato filling should be warm and creamy.