In 9"x9" baking pan (22cm X 22cm) - or see the link in notes to use a different size pan - use coconut oil to oil the pan making sure the corners are well covered. Use parchment paper to line the pan leaving handles hanging over the edge to lift the 'cake' out of the pan easily after baking. Set aside. Set oven rack in center and preheat oven to 350F (177C).
For the dry ingredients: Reserve a few tablespoons of oats and chocolate chips for sprinkling on top, if desired. In a large mixing bowl, mix the oats, walnuts, coconut, sunflower seeds, chocolate chips, cinnamon, baking soda and salt. Set aside.
For the wet ingredients: Make sure to start with room temperature ingredients. In a medium mixing bowl, mash the bananas, then add the peanut butter, syrup, oil, water and extract. Use the masher to mix the ingredients, then whisk vigorously until all the wet ingredients come together and are smooth(ish).
Pour the wet ingredients into the dry ingredients. Using a sturdy wooden spoon and a strong arm, mix the ingredients throughly. Spoon into the prepared pan and spread the mixture evenly, making sure to push the batter into the corners of the pan. Sprinkle the reserved oats and chocolate chips on top.
Bake the 'cake' for 30-35 minutes, using a toothpick to check for doneness starting at 30 minutes. The 'cake' is done when the top is golden and the center slightly springs back when gently pressed. The toothpick will come out clean or with very few crumbs, yet with some chocolate holding on to it. Cool completely (very important), then use the parchment as handles to lift the 'cake' out of the pan. (See notes below on cutting). The pieces will be slightly crumbly and very moist. Store at room temperature for up to five days, covered. These freeze beautifully too for up to two weeks.
NOTE: If you find your bars are a bit crumbly, an overnight rest in the fridge will firm the bars up a bit.