Butter a 9 x 5 x 3 inch loaf pan and preheat the oven to 350 degrees
With an electric mixer, cream the butter and sugar together.
Add the bananas, egg yolks, vanilla, lemon juice and baking soda.
Stir in flour with a spatula.
In a separate bowl, beat the egg whites with an electric mixer until very soft peaks form or until stiff. With a spatula, gently fold the egg whites into the rest of the banana mixture. (this is the trick to making your bread super moist rather than firm and dry)
Pour the mixture into the well greased pan and then sprinkle the crushed walnuts on top. Bake for 50 minutes, rotating the pan halfway through baking. Let cool on wire rack for about 5 to 10 minutes before serving. (mot recipes say cool completely but I couldn't resist, and I didn't taste a difference regardless)
Recipe by A Sue Chef at http://www.asuechef.com/moist-banana-nut-bread/