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.