Begin by peeling and cutting your sweet potatoes into large chunks. Place the slices into a pot and cover them with water. Bring the water to a boil over medium-high heat, and let the sweet potatoes cook for 15–20 minutes, or until they are fork-tender.

Once the sweet potatoes are fork-tender, drain them in a colander and return them to the pot. Using a potato masher or a handheld mixer, mash the sweet potatoes until they are smooth and free of lumps.

In a large mixing bowl, combine the mashed sweet potatoes with softened butter, brown sugar, milk, eggs, vanilla extract, and salt. Use a whisk or electric mixer to blend everything together until the mixture is creamy and well-combined.

In a separate bowl, stir together the flour, granulated sugar, ground cinnamon, and chopped pecans. Pour in the melted butter and mix everything with a fork until it resembles a crumbly texture.

Preheat your oven to 350°F (175°C). Pour the sweet potato mixture into a greased 9x13 inch baking dish, spreading it out evenly with a spatula. Sprinkle the crunchy topping generously over the sweet potato layer.

Place the casserole in the preheated oven and bake for 30–35 minutes until the topping is golden-brown and edges are bubbling.

Once baked, remove the casserole from the oven and let it cool for about 5 minutes.