Preheat oven to 350º

In a small bowl, whisk together flour, baking powder, baking soda and salt; set aside.

Combine sugar, melted butter, sour cream, eggs and vanilla in a large mixing bowl; beat until well blended. Stir in bananas. Add flour mixture to banana mixture, stirring just until moistened. Mix in chocolate chunks and nuts.

Spoon batter into an 8 ½ x 4 ½ x 3-inch loaf pan coated with baking spray with flour. Bake for 1 hour and 5 minutes or until a wooden pick inserted in center comes out clean.

Cool 10 minutes in pan on a wire rack; remove from pan, and cool completely on a wire rack before cutting.