Preheat oven to 350 degrees F. Lightly coat a 9 x 5-inch loaf pan with butter or vegetable spray. Whisk together the flour, salt and baking soda in a bowl. In another bowl beat the butter and sugars until well combined. Beat in the egg, bananas, buttermilk and vanilla. Beat in the dry ingredients and then the chocolate chips. Spoon into the loaf pan; bake 60-70 minutes, or until tooth pick inserted into the centre of the loaf pulls out clean. Cool in the pan on a baking rack 15 minutes, then unmould.