Preheat the oven to 350°F/180°C. Make sure that the oven rack is in the center of the oven. Prepare an 8x8-inch (20x20-cm) pan with parchment paper and a bit of spray oil. Set aside.
Prep the ingredients. Make sure that you have mashed sweet potatoes. Make the flax egg by combining the ground flax seeds with the hot water in a small, heat proof bowl. Stir together and set aside to gel. Melt half the chocolate chips in a small heat proof bowl and also set aside.
Make the brownies. Into a large mixing bowl, combine the mashed sweet potatoes, melted chocolate, plant milk, vanilla, and both sugars. Using a spatula or a whisk, mix this all together. Now add the flour, cocoa powder, baking powder, and salt. Stir again with a spatula. This is thick brownie batter!
Transfer. Transfer the brownie batter to the prepared pan, using a spatula to gently press the batter into the corners and even out the top. Sprinkle the remaining half of chocolate chips on top.
Bake. Bake for 35 minutes uncovered. The edges will slightly pull away from the sides and a toothpick inserted into the brownies 2 inches from the edge will pull out clean when the brownies are done baking. Let the brownies cool for 15 to 30 minutes before slicing and serving. Enjoy!
