Preheat oven to 350 degrees Grease muffin tins or place muffin liners in tins.
Cream the butter and sugar together, beat at least 5 minutes until it's well blended and not gritty looking. Add the eggs and mix until well blended.
Place the sour cream and baking soda in a small bowl, whisk together, let sit a few minutes until sour cream is puffed up and looks risen. Add to the butter mixture and beat well.
Add mashed bananas and vanilla to the bowl, mix until thoroughly incorporated. Place the flour and baking powder in a medium bowl, whisk to combine. Add to the batter, mix until just incorporated. Fold in chocolate chips and pecans.
Fill muffin tins 3/4 full with batter. Sprinkle batter with extra chopped pecans if desired. Bake 25 -30 minutes.
Recipe makes 1 1/2 dozen muffins