Preheat the oven to 325℉. Line a 8x8 or 9x9 square pan with parchment paper or spray with cooking spray.
Prick the medium sweet potato multiple times and microwave it for 5 minutes. Carefully cut it in half. Test for doneness with a knife. If done, set it aside. If it's still hard, microwave for additional 2 minutes. Set aside to cool.
Add the gluten-free flour, cocoa powder, salt, espresso powder and baking powder to a medium bowl. Mix together so that there are no white lumps of flour. Set aside.
Microwave the butter, in a large bowl, approximately 45-60 seconds to melt it.
Add half of the chopped chocolate to the melted butter and stir until the chocolate is melted.
Add the sugar to the melted butter and chocolate and stir until combined.
Mash the cooled sweet potato with a fork. Add ½ cup of the mashed sweet potato to the wet mixture and stir until combined.
Add the eggs and vanilla to the wet mixture and stir until combined.
Add the dry ingredients to the bowl and stir only until combined.
Fold in the other half of the chopped chocolate.
Pour into the baking pan. Bake at 325℉ for 35-40 minutes. Check at 35 minutes. Gluten free brownies will typically need a few more minutes than regular brownies. A toothpick will not come out clean but it should not be coated either.
Let the brownies completely cool before cutting.
Optional: sprinkle flaked salt or cocoa powder on top for extra decoration.