- Beat butter at medium speed with an electric mixer until creamy; gradually add sugar, beating well. Add eggs, banana, and vanilla, beating until blended.
- Stir together flour, soda, and salt. Add flour mixture to banana mixture alternately with buttermilk, beginning and ending with flour mixture; beat at low speed until blended after each addition. Stir in morsels.
- Place paper baking cups in muffin pans, and coat with cooking spray; spoon batter into pans, filling cups two-thirds full.
- Bake at 350° for 17 minutes. Remove cupcakes from pans immediately, and cool on wire racks. Spread with frosting, if desired.