Prepare muffin tin with tin liners or spray with Pam for Baking.
Smash bananas in a bowl. Add flour, sugar, baking soda and mix until combined. Add melted butter and mix until combined, then add egg and vanilla and mix until combined. Add peanut butter chips and walnuts and mix until combined.
Spoon heaping mixture into mini-muffin tin and back approximately 18 minutes.
Recipe by Tout va bien! (tm) at https://christymajors.com/bloggerclue-society-banana-peanut-butter-chip-muffins/