Pre-heat your oven to 350°F / §80°C. Lightly grease your casserole dish.
Place the cubed sweet potatoes into a large pot and cover with water. Bring to a boil, then reduce the heat and simmer for about 15 minutes, until fork tender.
Drain the sweet potatoes and add back to the same pot. Add the coconut milk, cinnamon, nutmeg, vanilla, salt, and maple syrup. Use a potato masher to mash and mix well.
Spread the sweet potato mixture into your prepared casserole dish.
In a medium-sized bowl, combine the spelt flour, coconut sugar, coconut oil, and salt. Use a silicon spatula or your fingers to work the oil into the flour and sugar to make a crumble mixture. Add the chopped pecans.
Evenly sprinkle the pecan crumble over top of the sweet potato mixture.
Place your sweet potato casserole into the oven and bake for 30-40 minutes, until the crumble topping is browned and crisp on top.
Remove from the oven and let stand for 10 minutes before serving.