In a large bowl, combine the flour, sugar, baking powder, baking soda and salt. Combine the egg, sour cream, butter and vanilla. Stir into dry ingredients just until moistened. Fold in chocolate chips., Fill greased or paper-lined muffin cups three-fourths full. Bake at 350degrees for 18-20 minutes or until a toothpick inserted in the center comes out clean. Cool for 5 minutes before removing from pan to a wire rack.