Preheat oven to 350
In a large pot, place the sweet potatoes on the bottom and fill with water until the potatoes are completely covered. Boil until the potatoes are able to be easily pierced with a fork
Once the potatoes are cooked, remove from the water and allow them to cool before peeling
Mash the sweet potatoes in a large bowl until there are no lumps left. Add egg, cinnamon, salt, and 1 tbsp of butter and combine
Using cooking spray or butter, grease a small baking dish and add the sweet potato mixture to it
In a small bowl, combine brown sugar, chopped nuts, shredded coconut, and remaining tbsp of butter. Sprinkle over the top of the casserole
Loosely cover the top of the casserole dish with foil to prevent the topping from burning, and bake for 20 minutes