Preheat oven to 400 degrees F. Line a small baking sheet with aluminum foil. Use a fork to poke holes in the sweet potato in 4 or 5 spots. Once preheated, bake the sweet potato on the baking sheet for 45-55 minutes, or until you see the juices start to emerge from the poked holes. A fork should easily be able to pierce through the sweet potato. Let the sweet potato cool until easy to handle. Lower the oven temperature to 325 degrees F.

Peel the sweet potato and discard skin. Add sweet potato chunks and 3 tablespoons milk of choice to high speed blender or food processor and blend. If the sweet potato is chunky after blending, add an additional tablespoon of milk. Blend until completely smooth.

Add the wet ingredients (peanut butter, vanilla, egg) to the blender with sweet potato pureé and blend again. Mix until smooth and combined.

In a large bowl, whisk all dry ingredients except chocolate chips together. Add the wet ingredients to the dry ingredients and combine. Add chocolate chips (save a few for topping) and mix until combined.

Add a teaspoon or so of avocado oil or olive oil to a 10 inch cast iron skillet and use a paper towel to rub the oil around the bottom and sides of the skillet. Add the brownie batter to the skillet and use a spatula to spread it out into a even layer. Sprinkle with chocolate chips.

Bake in the preheated 325 degrees F oven for 35-40 minutes or until a toothpick inserted in the center comes out clean. Let cool for 5 minutes and then serve.