Prepare your muffin tin by lightly greasing or using paper muffin liners.
Peel and mash the bananas in a small bowl. Add a little lemon juice to prevent browning.
Combine the flour, baking soda, baking powder, and salt in a bowl.
Combine the oil, egg, peanut butter, and syrup/sugar in a mixing bowl and whisk until combined. Fold in the mashed bananas.
Fold in the dry ingredients (and chocolate chips, if using). Don't over mix the batter!
Cover and chill the batter for 30 minutes, if desired.
While batter is chilling, preheat the oven to 350ºF.
When ready to bake, scoop the batter into the muffin tin, filling each cup about 3/4 full.
Bake for 20-22 minutes, until golden on top and/or a toothpick inserted comes out clean.
Let cool for 5 minutes in then tin, then turn them out onto a wire rack to cool completely.