I've been using this recipe for years, adapting it here and there. The paper it's printed on is well-worn and crusted with numerous previous batter accidents.
You can find ground flax at bulk barn. Flax contains high levels of omega-3 fatty acids. You can also use it in seed form, but to get the full health benefits the seed should be ground before using.
3/4 cup butter
3/4 cup brown sugar
2 beaten eggs
5 smashed overripe bananas (about 2 1/2 cups)
2 cups whole wheat flour (you can also use all-purpose flour)
1/2 cup ground flaxseed
1/4 tsp salt
1 tsp baking soda
Combine dry ingredients in a large bowl. In a seperate bowl cream butter and brown sugar. Add eggs and smashed bananas, mix well. (I just peel and squish 'em with my hands above the bowl...it's more fun that way.) Add banana mixture into dry ingredients, stirring just to moisten. Pour batter into a greased 9x5 loaf pan. Bake at 350 degrees F for 60-65 minutes.