Preheat oven to 350 degrees. Line a 10” cake pan with parchment and set aside.
Combine coconut milk, eggs, maple syrup, vanilla, and ghee in a blender. Add sweet potato mash and blend again until smooth. Transfer contents to a large bowl.
In a separate bowl, add coconut flour, tapioca flour, cinnamon, salt, baking powder and mix until well combined. Add dry ingredients with blended wet batter and whisk until smooth. Fold in 1/2 cup or more coconut flakes.
Pour into cake pan. Sprinkle a handful chopped hazelnuts and remaining coconut flakes.
Bake for 50 minutes, cover will foil, then bake for 20-30 minutes more. The edges will be crispy brown. Check the middle to make sure it is spongy and a toothpick comes out clean. May need more time. Remove from oven and let cool.