How to Make It
In a large bowl, sift together the baking soda and salt, and set aside. In a large measuring cup, whisk the eggs and vanilla and set aside. Butter a 9 by 5-inch loaf pan, and preheat the oven to 350º.
Cream the butter and sugar in a stand mixer fitted with the paddle attachment or a hand mixer, until it starts to become light and fluffy. Gradually pour the egg mixture into the butter, while mixing, until all of the ingredients are incorporated. Slowly add the bananas, while mixing on low, then remove the bowl from the mixer.
With a rubber spatula, mix in the flour mixture until just incorporated. Fold in the flax meal, walnuts, and flax seeds, reserving a few of the nuts and seeds. Transfer the batter to the pan, and sprinkle the remaining walnuts and flax seeds on top of the batter. Bake until a toothpick inserted into the center of the bread comes out clean, about 40 to 55 minutes depending on your oven.
Cool the bread in the pan for 5 to 10 minutes. Turn the bread out of the pan to let it cool completely on a rack or towel, and store in an air-tight container or wrapped in plastic wrap.
Because store-bought flax seed meal lacks the nutritional value of whole flax seeds, it's best to make a fresh, coarse-ground flax seed meal just before you use it. Flax seed meal is easy to make with a with a food processor, clean coffee grinder, or blender. One cup of whole flax seeds yields about 1 2/3 cups of flax seed meal, so leave room for expansion (use any leftover flax seed meal in smoothies or sprinkled on top of cereal or yogurt).