Heat oven to 350 degrees F.

In a large bowl, stir together mashed sweet potatoes, sugar, butter, milk, vanilla and eggs until well combined. Pour and spread evenly into a casserole dish.

In a medium bowl using a pastry cutter or your fingers, combine pecans, brown sugar, flour and butter until mixture forms a coarse crumb. Sprinkle streusel evenly over top of casserole.

Bake 40 minutes until casserole is baked through and streusel topping is golden brown and bubbling.