Preheat oven to 350F and line an 8X11 baking dish with parchment paper.
Melt chocolate chips and coconut oil in a saucepan on low just until melted.
Combine the cassava flour, cocoa powder, maple sugar, and salt in a mixing bowl.
Whisk the egg and vanilla in a separate bowl.
Add melted chocolate and eggs to the large mixing bowl with dry ingredients. Mix to form a smooth batter.
Pour the batter into the parchment-lined dish.
Bake for 35-50 mins. The cooking time will vary depending on your pan as well as oven.
Cool before slicing.