Preheat the oven to 425°F and wash the sweet potatoes. Lightly prick the skin of each potato with a fork and place it on a baking sheet. Bake for 45 to 55 minutes, or until the sweet potatoes are tender and cooked through. Allow to cool then peel.
Preheat the oven to 350°F and lightly spray a 2-quart baking dish with nonstick cooking spray.
Place the peeled sweet potatoes in a large bowl and mash well. Add the sugar, vanilla, eggs, milk, peanut butter, and peanut powder and mix until smooth. Spread evenly into the prepared baking dish.
To make the streusel, combine the melted peanut butter, brown sugar, and flour in a small bowl. Press the mixture together using the back of a spoon. Keep pressing and mixing until the mixture is combined and crumbly. Add the peanuts and mix well. Sprinkle the topping over the sweet potato filling and bake for 30 to 35 minutes or until the center is mostly set. Serve hot.
