Preheat Oven: Preheat your oven to 350°F (175°C). Grease an 8x8-inch square baking dish or line it with parchment paper for easier removal.
Prepare Sweet Potato: Cook and mash the sweet potato until smooth. You can steam, boil, or bake it beforehand.
Mix Wet Ingredients: In a large bowl, combine the sweet potato puree, peanut butter, honey or maple syrup, and eggs. Mix well until smooth and creamy.
Add Dry Ingredients: Stir in the cocoa powder, all-purpose flour, salt, and baking powder until just combined. If using, fold in the dark chocolate chips.
Bake: Pour the brownie batter into the prepared 8x8-inch baking dish and spread it evenly. Bake for about 25-30 minutes, or until a toothpick inserted in the center comes out clean.
Cool and Slice: Allow the brownies to cool in the baking dish for about 10-15 minutes, then transfer them to a wire rack to cool completely before slicing into squares.