Preheat the oven to 175 C / 350 F. Grease a 24-cavity mini muffin tin or line 18 cavities with silicone liners.
Add the black beans, peanut butter, cocoa powder, maple syrup, egg, and vanilla extract to a food processor. Blend for about 1 minute, scraping down the sides, until completely smooth with no visible bean pieces.
Add the oats, protein powder, baking powder, and salt to the processor. Pulse 5 to 6 times until just combined, the batter should look thick and glossy, like brownie batter.
Fold in the mini chocolate chips by hand with a rubber spatula.
Spoon about 1 tbsp of batter into each muffin cavity, filling two-thirds full. This should give you about 18 bites.
Scatter a few extra chocolate chips on top of each one, pressing gently.
Bake for 15 to 18 minutes, until the tops look set and a toothpick comes out with a few moist crumbs, not wet batter.
Cool the bites in the tin for 10 minutes, then transfer to a wire rack to cool completely before storing.