Preheat oven to 350°
In a large stockpot, add peeled, cubed sweet potatoes with a pinch of salt into boiling water. Bring boil to high heat and then reduce heat and cook until potatoes are very tender (about 20 mins).
Drain potatoes in colander and transfer to a large mixing bowl.
Smash potatoes using a potato masher.
In a small bowl, slightly beat eggs then add to the potato mash.
Add milk, brown sugar, pumpkin pie spice, salt, melted butter, vanilla into the bowl with potato and egg mixture. Stir ingredients well until fully combined.
Transfer to an ungreased baking dish. Spread the mixture out so that it is even across the dish.
In a small bowl combine the ingredients for the topping - brown sugar, pecans, all-purpose flour, butter, salt, and cinnamon. Mix until it resembles coarse crumbs.
Sprinkle topping over the pumpkin mixture.
Place into the oven uncovered. Bake at 350° for 45 minutes.