Preheat oven to 180 C (355 F) and line a 20cm x 20 cm baking tray with baking paper, leaving an overhang of paper (this makes it easier to lift bars out once baked).
In a large bowl, combine rolled oats, ½ cup of the peanuts and salt. Mix to combine.
In a small bowl, mash banana. Add peanut butter, egg, golden syrup, oil, and vanilla extract and mix well. Add this to the oat mixture and mix well until combined. Spoon into prepared tray and bake for 20-25 minutes or until golden brown.
Once cool, use the overhang of baking paper to lift the bars out of the tray. Spread the melted chocolate over the bars and top with remaining peanuts.
Notes
1. These bars are just slightly sweet. If you would like them to be sweeter, add 1-2 extra tablespoons of golden syrup.