Preheat oven to 350 degrees F.

Pour yams into a large bowl and mash until desired smoothness. Leave some lumps if preferred.

Add granulated sugar, milk, egg, 3 tablespoons of butter, and vanilla to the yams. Mix thoroughly.

In a smaller bowl, combine brown sugar, flour, 2 tablespoons of softened butter, and stir with a fork until crumbly. Stir in pecans.

Pour yam mixture into a 9-inch baking dish. Top with the brown sugar mixture and bake for 30 minutes until golden brown and bubbling.