Preheat the oven to 350 °F (180 °C). Line a 12-mini muffin pan with mini paper liners oiled with cooking oil spray. Set it aside. You can also bake the recipe in a small 6-inch x 6-inch square pan lined with parchment paper.
Prick a large sweet potato with a fork, place it on a microwave-safe plate, and microwave it on high (1000W) for 5 minutes. Flip the potato and microwave it again for 3-5 minutes. The sweet potato is cooked when you can easily insert a pick in the center.
Let it cool down completely, then pack it in a measuring cup to measure ½ cup.
Place all the ingredients in the bowl of a food processor: sweet potato puree, maple syrup, peanut butter, cocoa, and optional vanilla if used.
Blend on high speed until it forms a dough. It's not liquid but relatively firm.
Fold in the chocolate chips if used, and pulse a few times to incorporate.
Roll dough balls and place on each mini hole, or press the whole brownie batter onto a 6-inch square pan.
Bake the brownie bites for 15-20 minutes at 350 °F (180 °C) until the top is dry, crackles and a toothpick inserted in the center comes out with a little wet batter on it, meaning the brownies are still moist.
Let the bites cool down on a cooling rack.
