Preheat your oven to 400 F. {Note: this temp is if you plan to make the sweet potato in the oven. If you are not using the oven to cook the potato, set the oven to 325 F instead.} See microwave option in notes.
*To bake the sweet potato in the oven, first wash, poke holes in the potato and then add to a baking sheet covered in parchment paper. Bake for 45-60 minutes, or until soft when poked through with a fork. Remove and let cool. Peel off the skin and mash into a 1 cup measuring cup. Then reduce the oven temperature to 325 F.
To an 8x8 pan (I recommend lightweight aluminum**), add a layer of parchment paper so it's covering the bottom and up the edges. This method will make it easier to remove the brownies from the pan. Or, alternatively, you can spray an 8x8 pan with baking spray or grease with a little coconut oil.
Next, prepare the flax eggs. To do this, grind 2 tablespoons of whole flax seeds*** in a coffee grinder. Then transfer to a small bowl and add 6 tablespoons water. Stir and let sit for at least 5 minutes. Or you can also use pre-ground flax seed.
In a large bowl, add the flour, baking powder, salt and cocoa powder. Stir until combined thoroughly.
Then add the sugar, flax eggs, coconut oil, vegan butter, mashed sweet potato and almond milk. Stir with a spoon until just starting to blend. Then using an electric mixer on LOW speed (or you can continue stirring with the large spoon), mix together until combined thoroughly. Don't overmix.
Fold in 1/2 cup of the chocolate chips and blend in evenly. Then using a spatula, transfer the batter to the 8x8 pan, in an even layer on top of the parchment paper. Sprinkle the remaining 1/4 cup chocolate chips evenly on top.
Bake uncovered (using an aluminum pan) at 325 F for 30-35 minutes. Check the brownies a minute or two before the timer ends. The edges of the brownies should be visibly baked through and the center will be set (not wiggly). You can also do a toothpick test- for fudgier brownies (not cakey), the toothpick should have a few crumbs on it when removed (not completely clean).
Let the brownies sit in the baking pan for at least 15 minutes to cool, then remove from the pan using the parchment paper. Let sit another 10 minutes before cutting. The brownies will get more firm as they sit.
Store in an airtight container in the fridge for up to a week. Serve these brownies with vegan vanilla ice cream or Homemade Almond Milk. Or you could even top them with some Vegan Caramel Sauce.