Beat the egg whites until they are stiff. In a bowl, beat the yolks together with the sugar, bananas, nuts and potato starch. Carefully fold the egg whites into the yolk mixture until it is well blended. Pour the batter into a greased tube pan***. Bake for 35-40 minutes, until the edges start to spring away slightly from the side of the pan. Remove the cake from the oven and let it cook completely. Remove the cake from the pan. If it seems moist to you, let it sit uncovered for an hour or so before you wrap it up.

*I used 4 ripe bananas that had been frozen in their skins. I defrosted them and then they slid right out of their skins, already soft enough to blended in with the batter.

**I actually used 1/2 cup walnut meal (finely ground walnuts) and about 1/2 cup of coarsely chopped walnuts, and I'll probably do that again next time I make this recipe

***I recommend using a silicone pan if you have one. I didn't have a tube pan so I used an 8x8 silicone brownie pan and a standard-sized tin bread ban.