Sweet Potato Casserole

Sweet potatoes (4-5 medium sweet potatoes)

Butter (softened, 1/2 cup)

Sugar (2/3 cup)

Vanilla extract (1 tsp)

Milk (1/3 cup)

Eggs (2)

Melted butter (1/3 cup)

Brown sugar (1 cup)

Flour (1/2 cup)

Pecans (chopped, 1 cup)