01 -  Preheat oven to 350°F. Lightly grease a 9x13-inch baking dish. 
 02 -  In a large saucepan, cover sweet potato cubes with water. Bring to a boil and simmer for 15 to 20 minutes, until fork-tender. Drain thoroughly. 
 03 -  Transfer drained sweet potatoes to a large mixing bowl. Mash until smooth with a potato masher. Add melted butter, milk, brown sugar, eggs, vanilla extract, cinnamon, and salt. Stir until creamy and fully incorporated. 
 04 -  Spread the sweet potato mixture evenly into the prepared baking dish. 
 05 -  In a separate bowl, combine flour, brown sugar, cinnamon, and salt. Add melted butter and mix until crumbly. Fold in chopped pecans. 
 06 -  Sprinkle the pecan streusel evenly over the sweet potato layer. 
 07 -  Bake for 25 to 30 minutes until the topping is golden and crisp. 
 08 -  Allow to cool for 10 minutes before serving.