Mix all of the ingredients together in a large bowl, apart from the white chocolate (or vegan alternative).
Line a deep flat tray with baking paper. Spoon out the mixture and spread with a soft spatula, ensuring you get a nice even layer. Mark out where you want to cut the bars to make this easier once set.
Pop this in the oven at 180 for 15 minutes, checking to make sure the edges are not burning.
Leave to cool in the fridge for at least an hour before adding the topping. Once cooled, score down the lines to cut these into bars. I used a pizza cutter.
Melt the white chocolate (or vegan alternative) and drizzle over the bars in a diagonal pattern, then transfer them back into the fridge for another hour to set.
Once your flapjack bars have set you can freeze them or keep them in the fridge up to 7 days. I like to have some in the freezer so that I can grab one when I feel the need.