Peel and chop the sweet potato into 1-inch cubes. Boil for 15-20 minutes until fork-tender.

Drain and mash until smooth using a hand mixer or food processor. Let it cool to room temperature before using. (This step can be done in advance—see notes below.)

Preheat the oven to 350°F (175°C). Line an 8x8-inch baking pan with parchment paper.

In a medium bowl, whisk together the flour, baking soda, baking powder, salt, and cocoa powder.

In a large bowl, whisk the sweet potato puree, vegetable oil, granulated sugar, and brown sugar until well combined.

Add the eggs, buttermilk, and vanilla extract, mixing until smooth.

Gradually fold the dry ingredients into the wet ingredients, stirring between additions until a thick, glossy brownie batter forms.

Stir in the chocolate chips, then pour the batter into the prepared pan.

Bake for 25 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs. Let cool for at least 15 minutes before slicing.

Heat the heavy cream until hot but not boiling. Pour it over the chocolate chips in a heatproof bowl. Let sit for 2 minutes, then whisk until smooth.

Spread a thin layer of ganache over the cooled brownies. Slice and enjoy!