Preheat oven to 350°F (175°C) and line an 8x8-inch baking pan with parchment paper.
In a large bowl, mix the mashed sweet potatoes, almond butter, maple syrup, and vanilla extract until smooth.
Add cocoa powder, baking soda, and salt. Stir until well combined.
Fold in dark chocolate chips, if using.
Pour the batter into the prepared baking pan and spread evenly.
Bake for 25-30 minutes or until a toothpick inserted in the center comes out with a few moist crumbs.
Let cool before slicing and serving.