Preheat the oven to 180C/356F.
Line a 18.5cm X 18.5cm square brownie tin with a large piece of cling film with enough overhang to fold over the granola bars.
Combine the dry ingredients in a heat safe mixing bowl. Pour the combined mixture onto an oven tray and bake for 10-15 minutes. Baking is both to warm up the ingredients (so the peanut butter mixture won’t seize up when it hits cold nuts) and to toast the ingredients. You can toast them for longer if you’d like, but keep an eye on the quinoa flakes as they are prone to burning.
Five minutes before the nut mixture has finished cooking, combine the peanut butter and maple syrup in a small pan over a low medium heat. Use a heatproof silicon spatula to stir the mixture and ensure none is catching on the bottom of the pan.
Cook the mixture for around 4 minutes. First, it will look grainy and like the peanut butter is separated from the syrup. Next, it will come together and look glossy. If you draw a line in the mixture with your spatula, it should take a second for the mixture to melt back together.
As soon as little bits of cooked peanut butter start to form (they will look like little clumps) take the mixture off the heat.
Carefully decant the hot nut and quinoa flakes back into the bowl, then pour over the hot peanut butter mixture. Work quickly to coat all the mixture in the peanut butter – this is what will hold your muesli bars together, so everything needs to be coated and combined.
Once you’re happy, pour the mixture into the lined tin. Place the overhanging pieces of film down over the granola bars, then use the base of a smaller container (I use a square Tupperware) to press the bars down firmly and evenly into the tray. You need to use pressure so that the bars stay together in bar form once cooled.
Carefully remove the cling film cover so that the bars don’t sweat and allow them to cool. Allow the bars to cool completely before slicing in 10-12 bars. I slice the square in half through the centre, then into individual bars - 5 or 6 per half.
You can store the bars as a slice in the fridge or cut them up and store them in individual containers.