Optional: 1/4 cup shredded coconut or coconut flakes
Preheat oven to 350 degrees. Wash sweet potatoes and poke a couple of holes in them with a fork.
Place sweet potatoes on a parchment lined baking sheet and cook for 50-75 minutes (depending on the size of the potatoes- check at 50 minutes for smaller potatoes). Potatoes are done when you can easily insert a fork into the middle.
Wait until sweet potatoes are cool enough to handle, and then remove the skin. In a medium bowl, mash potatoes with maple syrup or honey, coconut milk, and cinnamon.
Spray an 8x8 or 9x9 inch baking dish with cooking spray and add potato mixture.
In now-empty mixing bowl, stir together topping ingredients. Spread topping over sweet potatoes. Bake casserole at 350 degrees for 20 minutes, or until topping is lightly brown. Remove from oven and sprinkle with coconut flakes, if using. Serve warm.
If baking sweet potato casserole straight from the fridge, cover with aluminum foil and bake for 50-60 total minutes at 350 degrees, until heated through.