Preheat the oven to 350 degrees.
Peel and cook a sweet potato. You can do this by boiling or baking it. You need 1 cup of cooked sweet potato for the brownies.
Using a food processor with a large blade, or a blender.
Spoon the cooked sweet potato into the food processor or blender.
Add the pitted dates (make sure they are soft). If they are not soft, boil 1 cup of water and add the dates; allow them to soften for about 10 minutes. Drain and then add to the food processor or the blender.
Now, add the maple syrup and nut butter.
Blend the ingredients until smooth.
If your dates are dry, you may need to add a Tablespoon or two of water.
In a separate bowl, combine the oat flour, unsweetened cocoa powder, and baking soda.
Pour the blender contents into the dry ingredients, scraping the blender's contents into the bowl with the dry ingredients.
Stir until combined. The batter will be thick.
Prepare an 8 X 8 pan with parchment paper.
Brush a little water into the base of the pan to make the parchment paper fit perfectly; the paper will stick to the pan and make it tighter.
Using a spatula, spread the brownie batter into the bottom of the pan, pushing it into the corners.
If the batter is sticky, lightly dip the spatula in water to keep it from sticking.
Sprinkle with sea salt if desired.
Bake for 30 minutes.