Preheat oven to 350°F/180°C. Grease a muffin pan or line with cupcake liners.
In a large bowl mix together flour, baking powder, baking soda, and cinnamon.
In a medium bowl, whisk together eggs and sugar until well combined. Add bananas, peanut butter, and sour cream and whisk until combined. Pour the egg mixture into the flour mixture and mix as little as possible, just until combined. Stir in chocolate/peanut butter chips if using.
Divide mixture between muffin cups, filling about ¾ full. Bake for 15-20 minutes or until a toothpick inserted into the center of a muffin comes out clean. Transfer to a wire rack and allow to cool for 10 minutes before removing from pan.
Store muffins in the fridge for up to 5 days. Bring to room temperature before serving. Muffins can be frozen for up to 2 months. Thaw overnight in the fridge or for an hour at room temperature.