Preheat Oven: Preheat your oven to 350°F (175°C). Grease or butter a 9x13-inch casserole dish.
Mash the Sweet Potatoes: In a large mixing bowl, mash 5 cups of cooked sweet potatoes (or use 2 cans of drained sweet potatoes) until smooth. Use a potato masher for a chunkier texture or a hand mixer for a creamier consistency. This should take about 3-5 minutes.
Make the Sweet Potato Mixture: Add 2 large eggs, ½ cup milk, ¾ cup granulated sugar, 4 tablespoons melted butter, 1 teaspoon vanilla extract, and ½ teaspoon salt to the mashed sweet potatoes. Stir well until everything is fully combined and smooth.
Spread into Dish: Spread the sweet potato mixture evenly into the prepared 9x13 casserole dish.
Prepare the Pecan Topping: In a medium bowl, combine 1 cup chopped pecans, 1 cup light brown sugar, ⅔ cup all-purpose flour, 6 tablespoons melted butter, and ¼ teaspoon ground cinnamon (optional). Stir until the mixture resembles wet sand (about 1-2 minutes).
Add the Topping: Evenly sprinkle the pecan topping over the sweet potato mixture.
Bake: Bake uncovered for 35-40 minutes, or until the top is golden brown and the sweet potatoes are fully cooked. Let it cool for about 5 minutes before serving.