Preheat oven to 350°F and lightly grease a mini muffin tin or line with silicone cups.
Blend black beans, zucchini (if using), eggs, oil (or nut butter), vanilla, salt, cocoa powder, maple syrup, baking powder, and oat flour until smooth.
Stir in (or sprinkle on top) mini chocolate chips if using, then scoop batter into mini muffin wells, filling almost to the top.
Bake 12–16 minutes, until centers are set, then let cool in the pan for at least 10 minutes before transferring to a rack.
