Preheat your oven to 425°F (220°C). Scrub the sweet potatoes thoroughly and poke several holes in them with a fork. Place the sweet potatoes directly on the oven rack or a baking sheet. Bake for 40-50 minutes until they are tender when pierced with a knife, and the skin is slightly wrinkled.

Once baked, remove them from the oven and let them cool until comfortable to handle.

After they have cooled slightly, carefully peel off the skin and place the flesh into a large mixing bowl. Lower the oven temperature to 350°F (177°C).

Using a fork or potato masher, mash the sweet potatoes until smooth, ensuring there are no lumps.

In the bowl with the mashed sweet potatoes, add whole milk, large eggs, granulated sugar, melted salted butter, salt, vanilla extract, and ground cinnamon. Use an electric mixer to combine until smooth.

Grease a 9x13-inch baking dish and pour the mixture into it, spreading it evenly.

In a separate bowl, combine brown sugar, all-purpose flour, and chopped pecans. Mix in softened butter until it resembles coarse crumbs.

Spread the pecan streusel topping evenly over the sweet potato filling.

Bake in the preheated oven at 350°F (177°C) for 40-45 minutes, until the filling is set and the streusel is golden brown.

Allow to cool for about 10 minutes before serving.