Preheat oven to 350°. Grease a loaf pan and set aside.
In a medium bowl, mash bananas. Add eggs and whip until smooth. In a large bowl, cream butter and sugar until pale and fluffy. Add banana and egg, stirring to incorporate.
Sift together flour, baking soda, and baking powder, then gently stir dry ingredients into wet, being careful not to over-mix. If adding chocolate chips or raspberries, add after combining wet and dry ingredients. Pour into prepared loaf pan and bake for 50-60 minutes or until tester inserted into the middle of the loaf comes out clean.