Preheat oven to 350°F (175°C). Line an 8x8-inch baking pan with parchment paper.
In a large bowl, vigorously whisk together the mashed sweet potato, creamy nut butter, and pure maple syrup until completely smooth.
Sift the cocoa powder into the wet mixture and gently fold with a spatula until just combined. Do not overmix.
Pour the thick batter into the prepared pan and smooth the top evenly.
Bake for 28-32 minutes until the edges are set. The center will remain slightly soft.
Allow to cool completely in the pan, then chill in the refrigerator for at least 1 hour before slicing into 9 squares.
