Preheat your oven to 350°F (175°C) and prepare a muffin tin with liners or spray.

In a large bowl, combine peanut butter, mashed bananas, sugar, and eggs. Whisk until smooth and creamy. Add vanilla extract if using.

In a separate bowl, whisk together flour, baking soda, and salt. Set aside.

Fold the dry ingredients into the wet mixture until just combined; avoid overmixing.

Scoop batter into muffin cups, filling them about two-thirds full. Optionally add chocolate chips or nuts.

Bake for 18-20 minutes until golden brown and a toothpick comes out clean.

Let muffins cool in the tin for 5 minutes before transferring to a wire rack to cool completely.