Preheat oven to 425℉.
In a stand mix beat bananas until soft.
Add sugar, egg, egg yolk, sourdough discard, vanilla extract, and greek yogurt. Mix until blended.
Add butter and mix.
In a separate bowl combine flour, baking soda, baking powder, salt.
Add dry ingredients to wet and mix until just combined.
Add chocolate chips and mix.
Line a muffin tin with liners, and scoop batter into liners. You should be able to get 12 muffins.
Bake for five minutes at 425℉.
Reduce heat to 350℉ and continue to bake for another 18-20 minutes, or until toothpick inserted comes out clean.
