Pierce potatoes with a fork in several places, and microwave on high power for about 7 minutes, until cooked through.
When potatoes are cool enough to handle, slice them open. Use a spoon to scoop out the flesh and transfer it to a small bowl. Discard the sweet potato skins.
Preheat the oven to 350℉. Line a 9-inch square baking dish with parchment paper and set aside.
In the bowl of a stand mixer fitted with a paddle attachment (or use an electric hand mixer and large mixing bowl), blend mashed sweet potato, coconut oil, eggs, maple syrup, and vanilla extract on medium-high speed until smooth.
Add oat flour, cocoa powder, baking soda, baking powder, and salt. Mix on low speed to combine. Using a spoon, gently fold in chocolate chips.
Pour the brownie batter into the prepared pan and use an offset spatula or the back of a spoon to spread into an even layer.
Bake in preheated oven for 25-30 minutes, until the top of brownies is set and a toothpick inserted into the center comes out almost clean.
Remove from oven and set the pan on a wire rack. Let brownies cool for at least 10 minutes before slicing. The cooler they are, the easier the sweet potato brownies are to cut into nice clean slices.
Notes
If possible, use Japanese sweet potatoes. The Japanese variation of sweet potatoes is sweeter than most sweet potato varieties in the U.S., making them an ideal ingredient for making desserts. Their texture is drier, firmer, and starchier too.
Use canned sweet potato puree. If fresh sweet potatoes aren’t available, you can substitute with 2 cups canned sweet potato puree instead. One pound of canned sweet potato puree is equal to 2 cups of fresh sweet potatoes. Be sure to use unsweetened puree.
Line the baking pan with parchment to prevent the brownies from sticking. For easier removal from the pan, leave some of the paper hanging over the sides.