Preheat oven to 350 degrees.
To make the mashed sweet potatoes:
In a medium-sized pot, over medium/high heat, add the cubed sweet potatoes.
Add the kosher salt and water to cover the sweet potatoes.
Bring the pot to a boil, reduce heat to medium and let simmer for about 15-20 minutes.
Sweet potatoes should be fork tender.
Drain sweet potatoes well.
Mash the sweet potatoes with a potato masher until well blended.
To Prepare the Sweet Potato Filling:
In a large bowl, combine well the mashed sweet potatoes, flax milk, agave, blackstrap molasses, and melted butter, egg, and pure vanilla extract.
Spray a 3-quart casserole dish with non-stick cooking spray.
Pour the sweet potato filling into the casserole dish. Set aside
To make the nut topping:
In a small bowl, combine the chopped pecans, brown rice flour, coconut sugar, and melted butter.
Sprinkle the nut topping on top of the sweet potato casserole.
Bake for about 25-30 minutes.