Vegan Cinnamon Streusel Sweet Potato Casserole

1 Preheat the oven to 400 degrees(F).
2 Wash the sweet potatoes and poke wholes in the sweet potatoes with a fork a few times. Then put them whole on a sheet pan in the oven and roast for 35-45 minutes or until they are very soft and the skin is peeling away. 
3 Once the sweet potatoes are done, let them cool for a few minutes so you can handle them. Reduce the heat of the oven to 375 degrees(F).
4 When you can handle the sweet potatoes, cut them down the center and peel off the skins, adding the potato to a large mixing bowl.
5 Mash all the potatoes with a fork or potato masher. Then add the vegan butter, non-dairy milk, brown sugar, vanilla and salt to the bowl. Whisk together to combine and make completely smooth. 
6 Then pour the sweet potatoes into an 8x8 inch casserole dish, smooth out evenly and set aside.
7 Now, make the streusel, in a medium sized mixing bowl, combine the flour, brown sugar, salt, cinnamon and pecans or walnuts. Then break up the softened butter with your fingers and press and pinch into the dry ingredients. 
8 Once the butter is fully incorporated, you can crumble it with your fingers. Then sprinkle the crumbles on top of the sweet potatoes in the casserole dish. 
9 Bake for 15 minutes or until the streusel topping is brown and crispy. Serve hot.