I used Bob's Red Mill All purpose Gluten Free Baking Flour and the bread turned out so good! My son who usually does not like to eat any of the gluten free recipes that I have made ate this and said that he loved it and had some more for his snack the next day! When I made this, I only had two bananas that I had on hand to add to the recipe, but you should use three to get the best Banana flavor! America's Test Kitchen suggested adding 1/2 Cup of plain yogurt, but I didn't have any and added about a 1/4 cup of milk to get the batter the right constancy. I suggest using the yogurt and see how it will turn out. As for the walnuts, I personally cannot have nuts, so they are optional. You could also add 1/2 cup Chocolate chips to have some chocolate in it if you wish too!