To make this easy banana bread recipe, start by greasing an 8-ounce mini loaf pan, small ramekin, or muffin tin with cooking spray. Then, preheat your oven to 350 F. Next, take 1/2 a single overripe banana and mash it up with a fork in a small bowl. Add in the oil, egg yolk, vanilla extract, and sugar, to the mashed banana and mix.