1. Preheat oven to 350 degrees. Line muffin pan with paper liners.
2. Cream the butter and sugar with a mixer. Add eggs and mix well.
3. Dissolvebaking soda in the sourcream. Let it "rise" for a minute, then add it to the butter and egg mixture. Mix well with beater on medium speed. Add bananas and blend in.
4. Add flour and baking powder together. Mix in thoroughly, but no longer than necessary. Add vanilla. Stir in chocolate chips by hand. Fill muffin cups. Bake for 25-30 minutes. Recipe makes approximately 1 1/2 dozen.