You can find the entire recipe for Banana Walnut Chocolate Chunk Cookies here. Preheat the oven to 375. Whisk together the flours, salt and baking soda. This recipe calls for 1 cup all purpose flour and 1/2 cup whole wheat flour. This combination helps to make a nice, denser cookie. In an electric mixer cream together the butter and sugars until light and fluffy. Add in the room temperature eggs and vanilla, then mix in the mashed banana. Slowly add in the flour mixture until just combined. At this point I take the bowl off the mixer and stir in the oats, chocolate chunks and walnut chunks by hand. This helps prevent the batter from forming too much glutten and will help keep the chocolate and walnuts "chunky" instead of broken down into little pieces by the electric mixer.