Preheat oven to 350°F. Line an 8" × 8" brownie pan with parchment paper.
Using a small or mini food processor, puree the beans, dates, potato, tahini, and coconut butter until smooth, and then add the maple syrup and milk and puree again.
Add the cocoa powder, sugar, arrowroot, vanilla bean powder, baking powder, baking soda, and sea salt to the processor and puree until combined. (If your processor is too small, transfer the date mixture to a bowl, and use a spatula to incorporate the dry ingredients.) Stir in the chocolate chips.
Transfer the mixture to the brownie pan, and spread evenly with a spatula. Bake for 22–24 minutes (brownies will firm with cooling and are more fudgy with less baking, so don’t overbake). Remove, let cool completely, frost if desired, and cut into squares.