Preheat the oven to 160°C and line a 20cm cake tin with baking paper and grease with cooking spray.
1. Mix the oats, sunflower and sesame seeds and walnuts in a non-stick pan and toast on medium heat, tossing the pan now and then to make sure it doesn’t burn.
2. Warm the peanut butter, honey and sugar in a saucepan, and stir until the peanut butter has melted and the sugar has dissolved.