Preheat oven to 350°F (175°C).
In a large bowl, combine oats, chocolate chips, walnuts, raisins, salt, and cinnamon (along with orange zest or citrus zest, if using). Stir together.
In a saucepan over medium heat, melt the peanut butter and honey. Once they have melted together, whip them together with a fork. Pour over the oat mixture and mix with a large wooden spoon until well combined. Towards the end this can get a little difficult to mix together, make sure to break up any lumps with the wooden spoon to mix in any. dry oats that may be left.
Line a 9-inch square baking pan with parchment paper. Spread the mixture in the dish, using your hands or a spatula to spread it evenly. Once the mixture is spread out, press the mixture down firmly. I find it’s easy to fold any extra baking paper down on top of the mixture and then press down with your hand as it prevents your hands from getting too sticky.
Bake for 20 to 25 minutes until golden brown.
Remove from the oven and leave to cool. Once cooled, carefully remove the entire block from the pan by lifting the edges of the parchment paper. Place them on a cutting board and cut them into small bars with a serrated knife. Store in an airtight container.
Now pack up, hit the trail and enjoy!