Preheat the oven to 350°F (175°C) and grease or line an 8x8-inch baking dish with parchment paper.
Melt the chocolate chips and oil in a microwave-safe bowl, stirring every 20-30 seconds until smooth.
Mix the mashed sweet potato, maple syrup, coffee, and vanilla extract in a large bowl until combined.
Stir in the melted chocolate mixture and mix until smooth and well combined.
In a separate bowl, whisk together the flour, cocoa powder, baking powder, and sea salt.
Gradually fold the dry ingredients into the wet mixture until just combined. Be careful not to overmix.
Pour the batter into the prepared pan and spread it evenly.
Bake for 25-30 minutes or until a toothpick comes out with a few moist crumbs. Let the brownies cool completely in the pan before adding the ganache.
For the Ganache:
Heat the heavy cream in a small saucepan over medium heat until it just begins to simmer (do not boil).
Pour the hot cream over the chocolate chips in a heat-safe bowl. Let it sit for 1-2 minutes to soften the chocolate.
Whisk the mixture until smooth and glossy. Stir in the vanilla extract if using.
Pour the ganache over the cooled brownies and spread evenly. Allow the ganache to set for about 30 minutes at room temperature or 15 minutes in the fridge before slicing.